[Windows Phone 7 Development and Hacking] voluptuary:
WARNING: Just like any other tools using the Samsung Diagnostic app to make registry changes there is a chance that your 3G/4G connections could get all bungled up. There are fixes known but you are doing this at your own risk so keep that in mind.

I know that there are easier ways to set theme and accent colors for 1st gen Samsung devices and if you want to use those go ahead but as far as I know there are currently no real easy ways to do this on 2nd gen devices so that's why I'm doing this.

As long as your device is unlocked in some way (Developer/Chevron/WindowsBreak/Other) you can get custom theme and accent colors on your Samsung phone.

1.) First install the WP Dev Tools and unlock your Samsung phone.

2.) Use Microsoft's Application Deployment Tool to send the XAP to your phone. Don't run it, delete after it has been deployed.

3.) Install the Diagnosis app by typing ##634# on the phone keypad.

4.) After the Diagnosis app starts type *#9908# and select 'Extra Accents' press 'Save' then 'Close' and RESTART your phone.

5.) Your phone now has more theme options!

6.) (optional) Press the 'thanks' button at the bottom of this post if it worked for you.

FOR COMPATABILITY REASONS EXTRA ACCENT COLORS ONLY APPEAR WHEN USING ENGLISH (US)

Current Extra Accents: GRAY, HTC GREEN, NOKIA BLUE, ZEBRA (black /w light/blood/deep sea/jungle, white /w dark/darker)

Current Themes: Darker, Blood, Deep Sea, Jungle

I also have an 'All Themes' xap now that will install all the accents/themes in one shot. In this xap 'Darker' is now 'Night'

!IMPORTANT UPDATE INFO!: I have edited all accents/themes in an effort to eliminate an error that can cause 3rd party apps to stop functioning and crash the theme system. A side effect of this is that custom accents will show up ONLY when the language is set to English (US). If you would like an additional language to be supported please post your language code and I will try to make a xap for you in my free time, for example English (US) is 0409.

Also, I have figured out how to move files with provxml's so custom accents will work with 3rd party apps with no additional steps needed on both 1st and 2nd gen devices. Do NOT re-apply any of these if you already have working custom extra accents via the old xap's or you will get duplicate entries in your accent colors and it could even crash the theme system.

IMPORTANT: If you updated to 8107 via Zune you may have also updated your phones firmware. If this is the case you will not be able to use this hack. I would suggest rolling back to 7720/7740 and updating via CAB Sender using the cabs in Heathcliff74's thread.

MORE IMPORTANT INFO: Custom themes also apply extra accent colors. You may also notice with custom themes that the keyboard color doesn't change when a new theme is applied. If this happens just restart your phone and the color should be correct. Currently 3rd party apps when using any of the original accents and a custom theme will default to a blue accent, this has been fixed in the 'All Themes' xap, since there are quite a few file operations when you click 'Save' wait a few seconds before selecting 'Close' in order for the settings to apply.

NOTE: For 2nd gen Samsung phones you may need to download the Wireless Manager from the Marketplace to restore your 3G/4G.

THANKS: Heathcliff74 - File deployer, reeg420 - custom theme starting point, daniel-t & poloche - info about 3rd party app accent fix