My sister pointed this link out to me:
If you click on the photo icon in the upper-right corner, you can load up a picture. Then you can use the little circles to identify the colors in the picture. It's pretty good, although I did have it give me some very odd results when I pointed it at metallics in pictures of minis I painted. Still, for those of you, who, like me, having trouble identifying colors or understanding color theory, it's useful.
It's a pretty useful color wheel, too, if you're trying to identify which colors go together or clash.