This is a step by step to how can you Modify the WP7 accent and background colors for WP7
first you need to unlock your phone using ChevronWP7
http://xdaforums.com/showthread.php?t=857127
and Install the registry editor
http://forum.touchxperience.com/viewtopic.php?f=20&t=593
to modify the accent colors use the Advanced Configuration
http://forum.touchxperience.com/viewtopic.php?f=11&t=590
Use the registry editor to modify the background of the dark theme go to those Keys and change the value to your favorite color in HEX
[HKLM\ControlPanel\themes\1\Basethemecolor]
[HKLM\ControlPanel\themes\1\TextHighContrast]
[HKLM\ControlPanel\themes\1\TextBackGround]
[HKLM\ControlPanel\themes\1\pageBackGroundColor]
[HKLM\ControlPanel\themes\1\SysTrayBackGroundColor]
You might also need to change the font Color
[HKLM\ControlPanel\themes\1\TextNeutralColor]
[HKLM\ControlPanel\themes\1\ListPickerBackgroundPressed]
[HKLM\ControlPanel\themes\1\ContrastColor]
to modify the light theme back ground color:
[HKLM\ControlPanel\themes\0\Basethemecolor]
[HKLM\ControlPanel\themes\0\TextHighContrast]
[HKLM\ControlPanel\themes\0\TextBackGround]
[HKLM\ControlPanel\themes\0\pageBackGroundColor]
[HKLM\ControlPanel\themes\0\SysTrayBackGroundColor]
You might also need to change the font Color
[HKLM\ControlPanel\themes\0\TextNeutralColor]
[HKLM\ControlPanel\themes\0\ListPickerBackgroundPressed]
[HKLM\ControlPanel\themes\0\ContrastColor]
to get the colors in Hex you can find some good color combination here
http://www.webdevelopersnotes.com/design/colour_combinations_for_web_pages.php3
first you need to unlock your phone using ChevronWP7
http://xdaforums.com/showthread.php?t=857127
and Install the registry editor
http://forum.touchxperience.com/viewtopic.php?f=20&t=593
to modify the accent colors use the Advanced Configuration
http://forum.touchxperience.com/viewtopic.php?f=11&t=590
Use the registry editor to modify the background of the dark theme go to those Keys and change the value to your favorite color in HEX
[HKLM\ControlPanel\themes\1\Basethemecolor]
[HKLM\ControlPanel\themes\1\TextHighContrast]
[HKLM\ControlPanel\themes\1\TextBackGround]
[HKLM\ControlPanel\themes\1\pageBackGroundColor]
[HKLM\ControlPanel\themes\1\SysTrayBackGroundColor]
You might also need to change the font Color
[HKLM\ControlPanel\themes\1\TextNeutralColor]
[HKLM\ControlPanel\themes\1\ListPickerBackgroundPressed]
[HKLM\ControlPanel\themes\1\ContrastColor]
to modify the light theme back ground color:
[HKLM\ControlPanel\themes\0\Basethemecolor]
[HKLM\ControlPanel\themes\0\TextHighContrast]
[HKLM\ControlPanel\themes\0\TextBackGround]
[HKLM\ControlPanel\themes\0\pageBackGroundColor]
[HKLM\ControlPanel\themes\0\SysTrayBackGroundColor]
You might also need to change the font Color
[HKLM\ControlPanel\themes\0\TextNeutralColor]
[HKLM\ControlPanel\themes\0\ListPickerBackgroundPressed]
[HKLM\ControlPanel\themes\0\ContrastColor]
to get the colors in Hex you can find some good color combination here
http://www.webdevelopersnotes.com/design/colour_combinations_for_web_pages.php3