Zandre Bran, the author of a really nice GNOME theme called Fancy sent us a tip regarding his theme.
Here's how he describes it:
I use three colors, one that is predominantly a more pastel blue for color menu windows and buttons. The second color is orange (taken in tooltip background) selection of items and progressbar. The third color is black for decorating the windows and panels gnome. The background color of the screens is neutral, light gray. What differentiates this from other theme is the two colors used (blue and orange) and their tonal variations between selection, pre-screening and active. Thus giving a very informal and visual clean.
Here's a screenshot with the Fancy Gnome theme:
You can download it @ Gnome-Look.
Note: to use Fancy, you need the latest Murrine engine available in Ubuntu 10.04 Lucid Lynx. For Ubuntu Karmic, you can get the latest Murrine from the WebUpd8 PPA.