Many people think Contrasting your Ads will make them look ugly and decrease your Click Though Rate (CTR) , yes this is true in most cases. But it totaly depends on your audience. If they are tech savvy, Blending might be the best option. Contrasting does make the Ads stand out a lot more. To Contrast, choose colors that stand out against the background of your site. Contrasting is recommended only for sites with dark background, so we suggest using a palette with white background, white borders, and blue titles. http://wmseo.com/2006/11/10/adsense-contrasting/
Contrasting works if it blends with the style of your site. See this page on life after death for instance.
The only way to decide between blending, contrasting and complementing (your words) is to use the adsense channels to TEST which works better.