Jen has some good suggestions for picking up a great color scheme for your Google AdSense Ads:

1. The complimentary technique - This would use new colors not currently on the page, but colors chosen to complement the colors that are. You can leave the border hidden and use the complementary colors for all the text, or use those complementary colors in the ad unit’s border and background, as well.

2. The matching technique - If your logo is green, you might try matching both the border and background of the ad unit to the same green, then use the page background color as the ad unit’s text color. You aren’t introducing new colors, but matching the on-page colors, and this makes the ad unit more noticeable than the blended technique. Link