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                                                                    EXHIBIT 10.4

            FOURTH AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT

                                January 29, 2004

         THIS AGREEMENT is made as of the 29th day of January, 2004, by and
among Color Kinetics Incorporated, a Delaware corporation (the "Company"), and
the holders of the Company's Series A, Series B, Series C, Series D, Series D-1,
Series E, and Series F Convertible Preferred Stock.

         WHEREAS, the Company entered into a Third Amended and Restated
Registration Rights Agreement dated December 14, 2001 (the "2001 Agreement")
with the holders of the Company's Series A, B, C, D, D-1, and E Convertible
Preferred Stock in connection with the sale of the Company's Series E
Convertible Preferred Stock to such holders;

         WHEREAS, the Company proposes to sell shares of its Series F
Convertible Preferred Stock, $.001 par value, to certain parties pursuant to the
terms of a Series F Preferred Stock Purchase Agreement and it is a condition to
the closing of such sale that this Agreement be executed and delivered by the
parties hereto;

         WHEREAS, the Company and the parties thereto have agreed to amend and
restate the 2001 Agreement and the individuals and entities who are not parties
to the 2001 Agreement have agreed to become a party thereto by entering into
this Fourth Amended and Restated Registration Rights Agreement;

         WHEREAS, this Agreement shall be deemed to be effective immediately
following the entering into of the Series F Preferred Stock Purchase Agreement
of even date herewith by the parties thereto;

         NOW, THEREFORE, the parties hereto hereby agree that the 2001 Agreement
is hereby amended and restated in its entirety as follows:

                  1.       Certain Definitions. As used in this Agreement, the
following terms shall have the following respective meanings:

                  "Commission" shall mean the Securities and Exchange
         Commission, or any other federal agency at the time administering the
         Securities Act.

                  "Common Stock" shall mean the Common Stock, $.001 par value,
         of the Company, as constituted as of the date of this Agreement.

                  "Conversion Shares" shall mean shares of Common Stock issued
         upon conversion of the Preferred Shares.

                  "Exchange Act" shall mean the Securities Exchange Act of 1934,
         as amended, or any similar federal statute, and the rules and
         regulations of the Commission thereunder, all as the same shall be in
         effect at the time.

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                  "Preferred Shares" shall mean the shares of the Series A
         Convertible Preferred Stock, the Series B Convertible Preferred Stock,
         the Series C Convertible Preferred Stock, the Series D Convertible
         Preferred Stock, the Series D-1 Convertible Preferred Stock, the Series
         E Convertible Preferred Stock, and the Series F Convertible Preferred
         Stock.

                  "Registration Expenses" shall mean the expenses so described
         in Section 8.

                  "Restricted Stock" shall mean the Conversion Shares, excluding
         Conversion Shares which have been (a) registered under the Securities
         Act pursuant to an effective registration statement filed thereunder
         and disposed of in accordance with the registration statement covering
         them or (b) publicly sold pursuant to Rule 144 under the Securities
         Act.

                  "Securities Act" shall mean the Securities Act of 1933, as
amended, or any similar federal statute, and the rules and regulations of the
Commission thereunder, all as the same shall be in effect at the time.

                  "Selling Expenses" shall mean the expenses so described in
Section 8.

                  2.       Restrictive Legend. Each certificate representing
Preferred Shares or Conversion Shares shall, except as otherwise provided in
this Section 2 or in Section 3, be stamped or other wise imprinted with a legend
substantially in the following form:

                           "THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE
                  SECURITIES ACT OF 1933 OR ANY STATE SECURITIES LAWS AND MAY
                  NOT BE TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS IT HAS BEEN
                  REGISTERED UNDER SUCH ACT AND ALL SUCH APPLICABLE LAWS OR AN
                  EXEMPTION FROM REGISTRATION IS AVAILABLE."

A certificate shall not bear such legend if in the opinion of counsel
satisfactory to the Company (it being agreed that Foley Hoag LLP shall be
satisfactory) the securities represented thereby may be publicly sold without
registration under the Securities Act and any applicable state securities laws.

                  3.       Notice of Proposed Transfer. Prior to any proposed
transfer of any Preferred Shares or Conversion Shares (other than under the
circumstances described in Sections 4, 5 or 6), the holder thereof shall give
written notice to the Company of its intention to effect such transfer. Each
such notice shall describe the manner of the proposed transfer and, if requested
by the Company, shall be accompanied by an opinion of counsel satisfactory to
the Company (it being agreed that Foley Hoag LLP shall be satisfactory) to the
effect that the proposed transfer may be effected without registration under the
Securities Act and any applicable state securities laws, whereupon the holder of
such stock shall be entitled to transfer such stock in accordance with the terms
of its notice; provided, however, that no such opinion of counsel shall be
required for a transfer to one or more partners or members of the transferor (in
the case of a transferor that is a partnership or a limited liability company,
respectively) or to an affiliated corporation or entity (in the case of a
transferor that is a corporation or other entity).

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Each certificate for Preferred Shares or Conversion Shares transferred as above
provided shall bear the legend set forth in Section 2, except that such
certificate shall not bear such legend if (i) such transfer is in accordance
with the provisions of Rule 144 (or any other rule permitting public sale
without registration under the Securities Act) or (ii) the opinion of counsel
referred to above is to the further effect that the transferee and any
subsequent transferee (other than an affiliate of the Company) would be entitled
to transfer such securities in a public sale without registration under the
Securities Act. The restrictions provided for in this Section 3 shall not apply
to securities which are not required to bear the legend prescribed by Section 2
in accordance with the provisions of that Section.

                  4.       Required Registration. (a) At any time after the
earliest of (i) six months after any registration statement covering a public
offering of securities of the Company under the Securities Act shall have become
effective, (ii) six months after the Company shall have become a reporting
company under Section 12 of the Exchange Act, and (iii) November 4, 2005, the
holders of Restricted Stock constituting at least 40% of the total shares of
Restricted Stock then outstanding may request the Company to register under the
Securities Act all or any portion of the shares of Restricted Stock held by such
requesting holder or holders for sale in the manner specified in such notice,
provided that the shares of Restricted Stock for which registration has been
requested shall constitute at least 20% of the total shares of Restricted Stock
originally issued (or any lesser percentage if the reasonably anticipated
aggregate price to the public of such public offering would exceed $5,000,000).
For purposes of this Section 4 and Sections 5, 6, 13(a) and 13(d), the term
"Restricted Stock" shall be deemed to include the number of shares of Restricted
Stock which would be issuable to a holder of Preferred Shares upon conversion of
all Preferred Shares held by such holder at such time, provided, however, that
the only securities which the Company shall be required to register pursuant
hereto shall be shares of Common Stock, and provided, further, however, that, in
any underwritten public offering contemplated by this Section 4 or Sections 5
and 6, the holders of Preferred Shares shall be entitled to sell such Preferred
Shares to the underwriters for conversion and sale of the shares of Common Stock
issued upon conversion thereof. Notwithstanding anything to the contrary
contained herein, no request may be made under this Section 4 within 120 days
after the effective date of a registration statement filed by the Company
covering a firm commitment underwritten public offering in which the holders of
Restricted Stock shall have been entitled to join pursuant to Sections 5 or 6.

                  (b) Following receipt of any notice under this Section 4, the
Company shall immediately notify all holders of Restricted Stock from whom
notice has not been received and shall use its best efforts to register under
the Securities Act, for public sale in accordance with the method of disposition
specified in such notice from requesting holders, the number of shares of
Restricted Stock specified in such notice (and in all notices received by the
Company from other holders within 30 days after the giving of such notice by the
Company). If such method of disposition shall be an underwritten public
offering, the Company will designate the managing underwriter of such offering,
subject to the approval of the holders of a majority of the shares of Restricted
Stock to be registered, which approval shall not be unreasonably withheld or
delayed. The Company shall be obligated to register Restricted Stock pursuant to
this Section 4 on two occasions only, provided, however, that such obligation
shall be deemed satisfied only when a registration statement covering all shares
of Restricted Stock specified in notices received as aforesaid, for sale in
accordance with the method of disposition specified by the requesting

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holders, shall have become effective and, if such method of disposition is a
firm commitment underwritten public offering, all such shares shall have been
sold pursuant thereto, subject to underwriter's cutbacks due to the opinion of
the managing underwriter that the sale of all such shares would adversely affect
the marketing of the Restricted Stock to be sold (it being understood that the
obligation of the Company to register Restricted Stock pursuant to this Section
4 will not be satisfied if the underwriter's cutback reduces the shares of
Restricted Stock of holders to be registered by 10% or more).

                  (c) The Company shall be entitled to include in any
registration statement referred to in this Section 4, for sale in accordance
with the method of disposition specified by the requesting holders, shares of
Common Stock to be sold by the Company for its own account, except as and to the
extent that, in the opinion of the managing underwriter (if such method of
disposition shall be an underwritten public offering), such inclusion would
adversely affect the marketing of the Restricted Stock to be sold. Except for
registration statements on Form S-4, S-8 or any successor thereto, the Company
will not file with the Commission any other registration statement with respect
to its Common Stock, whether for its own account or that of other stockholders,
from the date of receipt of a notice from requesting holders pursuant to this
Section 4 until the completion of the period of distribution of the registration
contemplated thereby.

                  5.       Incidental Registration. If the Company at any time
(other than pursuant to Section 4 or Section 6) proposes to register any of its
securities under the Securities Act for sale to the public, whether for its own
account or for the account of other security holders or both (except with
respect to registration statements on Forms S-4, S-8 or another form not
available for registering the Restricted Stock for sale to the public), each
such time it will give written notice to all holders of outstanding Restricted
Stock of its intention so to do. Upon the written request of any such holder,
received by the Company within 30 days after the giving of any such notice by
the Company, to register any of its Restricted Stock, the Company will use its
best efforts to cause the Restricted Stock as to which registration shall have
been so requested to be included in the securities to be covered by the
registration statement proposed to be filed by the Company, all to the extent
requisite to permit the sale or other disposition by the holder of such
Restricted Stock so registered. In the event that any registration pursuant to
this Section 5 shall be, in whole or in part, an underwritten public offering of
Common Stock, the number of shares of Restricted Stock to be included in such an
underwriting may be reduced (pro rata among the requesting holders based upon
the number of shares of Restricted Stock owned by such holders) if and to the
extent that the managing underwriter shall be of the opinion that such inclusion
would adversely affect the marketing of the securities to be sold by the Company
therein, provided, however, that such number of shares of Restricted Stock shall
not be reduced if any shares are to be included in such underwriting for the
account of any person other than the Company or requesting holders of Restricted
Stock, and provided, further, however, that in no event may less than one-third
of the total number of shares of Common Stock to be included in such
underwriting be made available for shares of Restricted Stock. Notwithstanding
the provisions of the foregoing sentence, if the underwritten public offering of
the Company is an initial public offering, the total number of shares of
Restricted Stock to be included in such underwriting may be reduced to as low as
zero (0) if (i) the managing underwriter is of the opinion that such inclusion
of the Restricted Stock would adversely affect the marketing of the securities
to be sold by the Company and (ii) no other shareholder is allowed to include
shares of stock in such underwriting. Notwithstanding the provisions of this
Paragraph 5, the Company

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may withdraw any registration statement referred to in this Section 5 without
thereby incurring any liability to the holders of Restricted Stock.

                  6.       Registration on Form S-3. If at any time (i) a holder
or holders of Preferred Shares or Restricted Stock request that the Company file
a registration statement on Form S-3 or any successor thereto for a public
offering of all or any portion of the shares of Restricted Stock held by such
requesting holder or holders, the reasonably anticipated aggregate price to the
public of which would exceed $1,000,000, and (ii) the Company is a registrant
entitled to use Form S-3 or any successor thereto to register such shares, then
the Company shall use its best efforts to register under the Securities Act on
Form S-3 or any successor thereto, for public sale in accordance with the method
of disposition specified in such notice, the number of shares of Restricted
Stock specified in such notice. Whenever the Company is required by this Section
6 to use its best efforts to effect the registration of Restricted Stock, each
of the procedures and requirements of Section 4 (including but not limited to
the requirement that the Company notify all holders of Restricted Stock from
whom notice has not been received and provide them with the opportunity to
participate in the offering) shall apply to such registration, provided,
however, that the number of registrations on Form S-3 which may be requested and
obtained under this Section 6 shall be limited to two (2) within any one (1)
year period, and provided, further, however, that the requirements contained in
the first sentence of Section 4(a) shall not apply to any registration on Form
S-3 which may be requested and obtained under this Section 6.

                  7.       Registration Procedures. If and whenever the Company
is required by the provisions of Sections 4, 5 or 6 to use its best efforts to
effect the registration of any shares of Restricted Stock under the Securities
Act, the Company will, as expeditiously as possible:

                  (a) prepare and file with the Commission a registration
statement (which, in the case of an underwritten public offering pursuant to
Section 4, shall be on Form S-1 or S-3, if eligible, or other form of general
applicability satisfactory to the managing underwriter selected as therein
provided) with respect to such securities and use its best efforts to cause such
registration statement to become and remain effective for the period of the
distribution contemplated thereby (determined as hereinafter provided);

                  (b) prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
therewith as may be necessary to keep such registration statement effective for
the period specified in paragraph (a) above and comply with the provisions of
the Securities Act with respect to the disposition of all Restricted Stock
covered by such registration statement in accordance with the sellers' intended
method of disposition set forth in such registration statement for such period;

                  (c) furnish to each seller of Restricted Stock and to each
underwriter such number of copies of the registration statement and the
prospectus included therein (including each preliminary prospectus) as such
persons reasonably may request in order to facilitate the public sale or other
disposition of the Restricted Stock covered by such registration statement;

                  (d) use its best efforts to register or qualify the Restricted
Stock covered by such registration statement under the securities or "blue sky"
laws of such jurisdictions as the sellers

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of Restricted Stock or, in the case of an underwritten public offering, the
managing underwriter reasonably shall request, provided, however, that the
Company shall not for any such purpose be required to qualify generally to
transact business as a foreign corporation in any jurisdiction where it is not
so qualified or to consent to general service of process in any such
jurisdiction;

                  (e) use its best efforts to list the Restricted Stock covered
by such registration statement with any securities exchange on which the Common
Stock of the Company is then listed;

                  (f) immediately notify each seller of Restricted Stock and
each underwriter under such registration statement, at any time when a
prospectus relating thereto is required to be delivered under the Securities
Act, of the happening of any event of which the Company has knowledge as a
result of which the prospectus contained in such registration statement, as then
in effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in light of the circumstances then existing;

                  (g) if the offering is underwritten provide to the
underwriters: (i) an opinion dated such date of counsel representing the Company
for the purposes of such registration, addressed to the underwriters and
covering matters customarily included in such opinions and (ii) a letter dated
such date from the independent public accountants retained by the Company,
addressed to the underwriters and covering matters customarily included in such
letters; and

                  (h) make available for inspection by each seller of Restricted
Stock, any underwriter participating in any distribution pursuant to such
registration statement, and any attorney, accountant or other agent retained by
such seller or underwriter, all financial and other records, pertinent corporate
documents and properties of the Company, and cause the Company's officers,
directors and employees to supply all information reasonably requested by any
such seller, underwriter, attorney, accountant or agent in connection with such
registration statement.

                  For purposes of Section 7(a) and 7(b) and of Section 4(c), the
period of distribution of Restricted Stock in a firm commitment underwritten
public offering shall be deemed to extend until each underwriter has completed
the distribution of all securities purchased by it, and the period of
distribution of Restricted Stock in any other registration shall be deemed to
extend until the earlier of the sale of all Restricted Stock covered thereby and
120 days after the effective date thereof.

                  In connection with each registration hereunder, the sellers of
Restricted Stock will furnish to the Company in writing such information with
respect to themselves and the proposed distribution by them as reasonably shall
be necessary in order to assure compliance with federal and applicable state
securities laws.

                  In connection with each registration pursuant to Sections 4, 5
or 6 covering an underwritten public offering, the Company and each seller agree
to enter into a written agreement with the managing underwriter selected in the
manner herein provided in such form and containing such provisions as are
customary in the securities business for such an

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arrangement between such underwriter and companies of the Company's size and
investment stature.

                  8.       Expenses. All expenses incurred by the Company in
complying with Sections 4, 5 and 6, including, without limitation, all
registration and filing fees, printing expenses, fees and disbursements of
counsel and independent public accountants for the Company, fees and expenses
(including counsel fees) incurred in connection with complying with state
securities or "blue sky" laws, fees of the National Association of Securities
Dealers, Inc., transfer taxes, fees of transfer agents and registrars, costs of
insurance and fees and disbursements of one counsel for the sellers of
Restricted Stock, but excluding any Selling Expenses, are called "Registration
Expenses". All underwriting discounts and selling commissions applicable to the
sale of Restricted Stock are called "Selling Expenses".

                  The Company will pay all Registration Expenses in connection
with each registration statement under Sections 4, 5 or 6. All Selling Expenses
in connection with each registration statement under Sections 4, 5 or 6 shall be
borne by the participating sellers in proportion to the number of shares sold by
each, or by such participating sellers other than the Company (except to the
extent the Company shall be a seller) as they may agree.

                  9.       Indemnification and Contribution. (a) In the event of
a registration of any of the Restricted Stock under the Securities Act pursuant
to Sections 4, 5 or 6, the Company will indemnify and hold harmless each seller
of such Restricted Stock thereunder, each underwriter of such Restricted Stock
thereunder and each other person, if any, who controls such seller or
underwriter within the meaning of the Securities Act, against any losses,
claims, damages or liabilities, joint or several, to which such seller,
underwriter or controlling person may become subject under the Securities Act or
otherwise, insofar as such losses, claims, damages or liabilities (or actions in
respect thereof) arise out of or are based upon any untrue statement or alleged
untrue statement of any material fact contained in any registration statement
under which such Restricted Stock was registered under the Securities Act
pursuant to Sections 4, 5 or 6, any preliminary prospectus or final prospectus
contained therein, or any amendment or supplement thereof, or arise out of or
are based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading, and will reimburse each such seller, each such underwriter and each
such controlling person for any legal or other expenses reasonably incurred by
them in connection with investigating or defending any such loss, claim, damage,
liability or action, provided, however, that the Company will not be liable in
any such case if and to the extent that any such loss, claim, damage or
liability arises out of or is based upon an untrue statement or alleged untrue
statement or omission or alleged omission so made in conformity with information
furnished by any such seller, any such underwriter or any such controlling
person in writing specifically for use in such registration statement or
prospectus.

                  (b)      In the event of a registration of any of the
Restricted Stock under the Securities Act pursuant to Sections 4, 5 or 6, each
seller of such Restricted Stock thereunder, severally and not jointly, will
indemnify and hold harmless the Company, each person, if any, who controls the
Company within the meaning of the Securities Act, each officer of the Company
who signs the registration statement, each director of the Company, each
underwriter and each person who controls any underwriter within the meaning of
the Securities Act, against

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all losses, claims, damages or liabilities, joint or several, to which the
Company or such officer, director, underwriter or controlling person may become
subject under the Securities Act or otherwise, insofar as such losses, claims,
damages or liabilities (or actions in respect thereof) arise out of or are based
upon any untrue statement or alleged untrue statement of any material fact
contained in the registration statement under which such Restricted Stock was
registered under the Securities Act pursuant to Sections 4, 5 or 6, any
preliminary prospectus or final prospectus contained therein, or any amendment
or supplement thereof, or arise out of or are based upon the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, and will reimburse the
Company and each such officer, director, underwriter and controlling person for
any legal or other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, damage, liability or action,
provided, however, that such seller will be liable hereunder in any such case if
and only to the extent that any such loss, claim, damage or liability arises out
of or is based upon an untrue statement or alleged untrue statement or omission
or alleged omission made in reliance upon and in conformity with information
pertaining to such seller, as such, furnished in writing to the Company by such
seller specifically for use in such registration statement or prospectus, and
provided, further, however, that the liability of each seller hereunder shall be
limited to the proportion of any such loss, claim, damage, liability or expense
which is equal to the proportion that the public offering price of the shares
sold by such seller under such registration statement bears to the total public
offering price of all securities sold thereunder, but not in any event to exceed
the net proceeds received by such seller from the sale of Restricted Stock
covered by such registration statement.

                  (c)      Promptly after receipt by an indemnified party
hereunder of notice of the commencement of any action, such indemnified party
shall, if a claim in respect thereof is to be made against the indemnifying
party hereunder, notify the indemnifying party in writing thereof, but the
omission so to notify the indemnifying party shall not relieve it from any
liability which it may have to such indemnified party other than under this
Section 9 and shall only relieve it from any liability which it may have to such
indemnified party under this Section 9 if and to the extent the indemnifying
party is prejudiced by such omission. In case any such action shall be brought
against any indemnified party and it shall notify the indemnifying party of the
commencement thereof, the indemnifying party shall be entitled to participate in
and, to the extent it shall wish, to assume and undertake the defense thereof
with counsel satisfactory to such indemnified party, and, after notice from the
indemnifying party to such indemnified party of its election so to assume and
undertake the defense thereof, the indemnifying party shall not be liable to
such indemnified party under this Section 9 for any legal expenses subsequently
incurred by such indemnified party in connection with the defense thereof other
than reasonable costs of investigation and of liaison with counsel so selected,
provided, however, that, if the defendants in any such action include both the
indemnified party and the indemnifying party and the indemnified party shall
have reasonably concluded that there may be reasonable defenses available to it
which are different from or additional to those available to the indemnifying
party or if the interests of the indemnified party reasonably may be deemed to
conflict with the interests of the indemnifying party, the indemnified party
shall have the right to select a separate counsel and to assume such legal
defenses and otherwise to participate in the defense of such action, with the
expenses and fees of such separate counsel and other expenses related to such
participation to be reimbursed by the indemnifying party as incurred.

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                  (d)      In order to provide for just and equitable
contribution to joint liability under the Securities Act in any case in which
either (i) any holder of Restricted Stock exercising rights under this
Agreement, or any controlling person of any such holder, makes a claim for
indemnification pursuant to this Section 9 but it is judicially determined (by
the entry of a final judgment or decree by a court of competent jurisdiction and
the expiration of time to appeal or the denial of the last right of appeal) that
such indemnification may not be enforced in such case notwithstanding the fact
that this Section 9 provides for indemnification in such case, or (ii)
contribution under the Securities Act may be required on the part of any such
selling holder or any such controlling person in circumstances for which
indemnification is provided under this Section 9; then, and in each such case,
the Company and such holder will contribute to the aggregate losses, claims,
damages or liabilities to which they may be subject (after contribution from
others) in such proportion so that such holder is responsible for the portion
represented by the percentage that the public offering price of its Restricted
Stock offered by the registration statement bears to the public offering price
of all securities offered by such registration statement, and the Company is
responsible for the remaining portion; provided, however, that, in any such
case, (A) no such holder will be required to contribute any amount in excess of
the public offering price of all such Restricted Stock offered by it pursuant to
such registration statement; and (B) no person or entity guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
will be entitled to contribution from any person or entity who was not guilty of
such fraudulent misrepresentation.

                  10.      Changes in Common Stock or Preferred Stock. If, and
as often as, there is any change in the Common Stock or the Preferred Stock by
way of a stock split, stock dividend, combination or reclassification, or
through a merger, consolidation, reorganization or recapitalization, or by any
other means, appropriate adjustment shall be made in the provisions hereof so
that the rights and privileges granted hereby shall continue with respect to the
Common Stock or the Preferred Stock as so changed.

                  11.      Rule 144 Reporting. With a view to making available
the benefits of certain rules and regulations of the Commission which may at any
time permit the sale of the Restricted Stock to the public without registration,
at all times after 90 days after any registration statement covering a public
offering of securities of the Company under the Securities Act shall have become
effective, the Company agrees to:

                  (a) make and keep public information available, as those terms
are understood and defined in Rule 144 under the Securities Act;

                  (b) use its best efforts to file with the Commission in a
timely manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act; and

                  (c) furnish to each holder of Restricted Stock forthwith upon
request a written statement by the Company as to its compliance with the
reporting requirements of such Rule 144 and of the Securities Act and the
Exchange Act, a copy of the most recent annual or quarterly report of the
Company, and such other reports and documents so filed by the Company as such
holder may reasonably request in availing itself of any rule or regulation of
the Commission allowing such holder to sell any Restricted Stock without
registration.

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                  12.      Representations and Warranties of the Company. The
Company represents and warrants to you as follows:

                  (a) The execution, delivery and performance of this Agreement
by the Company have been duly authorized by all requisite corporate action and
will not violate any provision of law, any order of any court or other agency of
government, the Charter or By-laws of the Company or any provision of any
indenture, agreement or other instrument to which it or any or its properties or
assets is bound, conflict with, result in a breach of or constitute (with due
notice or lapse of time or both) a default under any such indenture, agreement
or other instrument or result in the creation or imposition of any lien, charge
or encumbrance of any nature whatsoever upon any of the properties or assets of
the Company (it being understood that the Company does not make the
representations contained in this Section 12(a) with respect to the
indemnification and contribution provisions of this Agreement).

                  (b) This Agreement has been duly executed and delivered by the
Company and constitutes the legal, valid and binding obligation of the Company,
enforceable in accordance with its terms subject to applicable bankruptcy,
fraudulent conveyance, insolvency, reorganization, moratorium and similar laws
affecting creditors' rights generally and by general equitable principles (it
being understood that the Company does not make any representations as to the
validity or enforceability of the indemnification and contribution provisions of
this Agreement).

                  13.      Miscellaneous.

                  (a) All covenants and agreements contained in this Agreement
by or on behalf of any of the parties hereto shall bind and inure to the benefit
of the respective successors and assigns of the parties hereto (including
without limitation transferees of any Preferred Shares or Restricted Stock),
whether so expressed or not, provided, however, that registration rights
conferred herein on the holders of Preferred Shares or Restricted Stock shall
only inure to the benefit of a transferee of Preferred Shares or Restricted
Stock if (i) there is transferred to such transferee at least 30% of the total
shares of Restricted Stock originally issued pursuant to the applicable
Preferred Stock Purchase Agreement to the direct or indirect transferor of such
transferee or (ii) such transferee is a partner, shareholder or affiliate of a
party hereto.

                  (b) All notices, requests, consents and other communications
hereunder shall be in writing and shall be delivered in person, mailed by
certified or registered mail, return receipt requested, or sent by telecopier or
telex, addressed as follows:

                  if to the Company or any other party hereto, at the address of
         such party set forth in the applicable Preferred Stock Purchase
         Agreement;

                  if to any subsequent holder of Preferred Shares or Restricted
         Stock, to it at such address as may have been furnished to the Company
         in writing by such holder;

or, in any case, at such other address or addresses as shall have been furnished
in writing to the Company (in the case of a holder of Preferred Shares or
Restricted Stock) or to the holders of Preferred Shares or Restricted Stock (in
the case of the Company) in accordance with the provisions of this paragraph.

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                  (c) This Agreement shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts.

                  (d) This Agreement may be amended or modified, and any
provision hereof may be waived, with the written consent of the Company and the
holders of at least fifty-one percent (51%) of the outstanding shares of
Restricted Stock.

                  (e) This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

                  (f) The obligations of the Company to register shares of
Restricted Stock under Sections 4, 5 or 6 shall terminate on the tenth
anniversary of the date of this Agreement.

                  (g) If requested in writing by the underwriters for the
initial underwritten public offering of securities of the Company, each holder
of Restricted Stock who is a party to this Agreement shall agree not to sell
publicly any shares of Restricted Stock or any other shares of Common Stock
(other than shares of Restricted Stock or other shares of Common Stock being
registered in such offering), without the consent of such underwriters, for a
period of not more than 180 days following the effective date of the
registration statement relating to such offering; provided, however, all
executive officers and directors of the Company shall also have agreed not to
sell publicly their Common Stock under the circumstances and pursuant to the
terms set forth in this Section 13(g).

                  (h) Notwithstanding the provisions of Section 7(a), the
Company's obligation to file a registration statement, or cause such
registration statement to become and remain effective, shall be suspended for a
period not to exceed 90 days in any 12-month period if (i) there exists at the
time material non-public information relating to the Company which, in the
reasonable opinion of the Company, should not be disclosed or (ii) if such
filing would materially and adversely affect a pending or scheduled public
offering of the Company's securities.

                  (i) The Company shall not grant to any third party any
registration rights more favorable than or inconsistent with any of those
contained herein, so long as any of the registration rights under this Agreement
remains in effect.

                  (j) If any provision of this Agreement shall be held to be
illegal, invalid or unenforceable, such illegality, invalidity or
unenforceability shall attach only to such provision and shall not in any manner
affect or render illegal, invalid or unenforceable any other provision of this
Agreement, and this Agreement shall be carried out as if any such illegal,
invalid or unenforceable provision were not contained herein.

                  (k) Purchasers of Series F Convertible Preferred Stock at an
Additional Closing (as defined in the Series F Convertible Preferred Stock
Purchase Agreement of even date herewith) may become a party hereto by executing
a counterpart signature page to this Agreement.

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<PAGE>

                  IN WITNESS WHEREOF, the parties hereto have executed this
Agreement as of January 29, 2004.

                                    COLOR KINETICS INCORPORATED

                                    By:  /s/ George Mueller
                                       ---------------------------------------
                                       George Mueller, Chief Executive Officer

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

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<PAGE>

            FOURTH AMENDED AND RESTATED REGISTRATION RIGHTS AGREEMENT
                     SIGNATURE PAGE OF PREFERRED STOCKHOLDER

The undersigned hereby executes this Fourth Amended and Restated Registration
Rights Agreement, authorizes this signature page to be attached to a counterpart
of said Agreement and agrees to be bound by said Agreement.

Name of Purchaser or Current Stockholder: ______________________________

Signature: _________________________________________________________

Name of Signer: ____________________________________________________

Title of Signer: _____________________________________________________

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