Okay, here's what I did. When I first started using AdSense, I made the backgound and text colors exactly the same as my side column colors.
At some point, I went through a period of time where my click-thrus just went right through the floor - one tenth of a percent.
So, I decided to start fooling around with using deliberately contrasting (read gaudy, outrageous) colors. My click-thru rate went back up, but since Google (as far as I know) won't tell you which colors have more click-thrus, I can't tell what really did it.
One problem with my layout is that I have very well-defined columns; I think that this helps people to tune ads out.
Personally, I think the cleverest use of AdSense ads is found in sites that work the ads directly into the text column, using the same colors, and then puts additional reference links right above the google ads. See this page -
http://www.sciencedaily.com/releases...0214081214.htm - for an example. Although, in going back, I see that they are using mildly contrasting colors now.