I've just upgraded to V6 which looks very nice but have not figured out how to change the background color of the window panes.
I read another post that you could configure things to use the windows background (which I have set to a shade of grey) and tried the "Windows Native" application look but this did not seem to do the trick.
I'm running Windows 7/x64 with Aero turned off (Keep the Video card running in 2D power saving mode)