Based on what Andrew has said, it seems that:
1) Window color: gray or off-white
2) Menu & toolbar area - gray
3) Window border matches menu and toolbar color
4) Selected items & widgets: blue/gray combination
5) Window buttons: tradtional (no colored buttons)
6) Icons: Blueish
The soft colors might look a little plain, but they are easy on the eyes. My
suggestions:
1) Add highlights to the window buttons when hovered over, perhaps with a
soft glow and the same color as widgets.
2) Add a stonger gradient or a glossy/3D look to the widgets and buttons. I
found some samples on Gnome-look:
http://gnome-look.org/CONTENT/content-pre2/118588-2.png
http://gnome-look.org/CONTENT/content-pre1/117808-1.jpg
This is only to show the effect; I am not suggesting these colors.
We should be able to create a modern looking theme that is both clean and
elegant without going overboard on the eyecandy. I don't know how to create
themes... perhaps I should read up on it.