We’ll never tell you what colors you can and.
You’re free to dabble in our hues, and experiment with all the colors of our rainbow. We’ll never tell you what colors you can and can’t use, as long as your users know they’re looking at “Ads by Yahoo!”. Maybe you want your ads to stand out from your page, or maybe you want them to blend in. You may not verge on a Van Gogh, and maybe your aesthetics don’t match Mondrian’s.
Original text search at: ypnblog.com/blog/2007/01/