A method for dyeing and reductively decolorizing keratin fibers, in particular human hair, comprising the following steps in the sequence indicated applying a cosmetic colorant containing at least one direct dye and/or at least one oxidation dye precursor to the keratin fibers allowing the colorant to act for a period of 5 to 60 minutes rinsing out the colorant applying a decolorizing agent to the keratin fibers, allowing the decolorizing agent to act at 20 to 45 °C for a period of 5 to 60 minutes, rinsing out the decolorizing agent, wherein the decolorizing agent is an agent for reductively decolorizing dyed keratin fibers, in particular human hair, containing, in a cosmetic carrier, (a) at least one compound of formula A[(CR 1 R 2)SO 2 M] q in which A represents N(R 3) 3-q R 1, R 2 represent, independently of one another, a hydrogen atom or a C 1 -C 6 alkyl group, R 3 represents identical or different functional groups selected from the group consisting of a hydrogen atom, a C 1 -C 20 alkyl group, a C 3 -C 8 cycloalkyl group optionally substituted by one to three C 1 -C 4 alkyl functional groups, M represents identical or different functional groups selected from a hydrogen atom or an equivalent of an alkali, alkaline-earth or metal ion, preferably sodium, potassium, 1⁄2 magnesium, 1⁄2 calcium, 1⁄2 zinc, or represents an ammonium ion (NH 4 +), q represents the number 2 or 3, and (b) at least one compound of formula A[(CR 1 R 2)SO 3 M] q in which A, R 1, R 2, R 3, M, and q have the same general meaning as in formula, wherein the selection of these variables in each specific case does not need to be the same for the compounds of formulas and. applying a cosmetic colorant containing at least one direct dye and/or at least one oxidation dye precursor to the keratin fibers allowing the colorant to act for a period of 5 to 60 minutes rinsing out the colorant applying a decolorizing agent to the keratin fibers, allowing the decolorizing agent to act at 20 to 45 °C for a period of 5 to 60 minutes, rinsing out the decolorizing agent, (a) at least one compound of formula A[(CR 1 R 2)SO 2 M] q in which A represents N(R 3) 3-q R 1, R 2 represent, independently of one another, a hydrogen atom or a C 1 -C 6 alkyl group, R 3 represents identical or different functional groups selected from the group consisting of a hydrogen atom, a C 1 -C 20 alkyl group, a C 3 -C 8 cycloalkyl group optionally substituted by one to three C 1 -C 4 alkyl functional groups, M represents identical or different functional groups selected from a hydrogen atom or an equivalent of an alkali, alkaline-earth or metal ion, preferably sodium, potassium, 1⁄2 magnesium, 1⁄2 calcium, 1⁄2 zinc, or represents an ammonium ion (NH 4 +), q represents the number 2 or 3, and A represents N(R 3) 3-q R 1, R 2 represent, independently of one another, a hydrogen atom or a C 1 -C 6 alkyl group, R 3 represents identical or different functional groups selected from the group consisting of a hydrogen atom, a C 1 -C 20 alkyl group, a C 3 -C 8 cycloalkyl group optionally substituted by one to three C 1 -C 4 alkyl functional groups, M represents identical or different functional groups selected from a hydrogen atom or an equivalent of an alkali, alkaline-earth or metal ion, preferably sodium, potassium, 1⁄2 magnesium, 1⁄2 calcium, 1⁄2 zinc, or represents an ammonium ion (NH 4 +), q represents the number 2 or 3, (b) at least one compound of formula A[(CR 1 R 2)SO 3 M] q in which A, R 1, R 2, R 3, M, and q have the same general meaning as in formula, wherein the selection of these variables in each specific case does not need to be the same for the compounds of formulas and.