I just stumbled across this site browsing Eris Design, and I thought that it might be helpful for anyone trying to fiddle with colors on their blog (because we all know that's the only thing I seem to think about...! LOL).
Click here to get to the page, that looks like this:
.bmp)
Find the little "window" at the bottom right-hand corner,
and click that.
Drag the colors on the left to the "window" on the right to see how colors might look on your blog. For instance, what will white text look like on top of a light blue background...

Play around, and have fun :)
Very useful widget!