you can modify the light or dark to be with the color you like using the registry Editor
but you need an unlocked phone by ChevronWP7
http://xdaforums.com/showthread.php?t=857127
and A registry editor
http://forum.touchxperience.com/viewtopic.php?f=20&t=593
to modify the dark theme go to those Keys and change the value to your taste of HEX color
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:
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
Enjoy