I have always used ad palettes that blended with my sites (within the TOS quidlines), and it worked well for me, but recently (over three months) CTR has dropped while impressions were still high.
Today I decided to change my ads on top level URLs to colors that clash (not irritate - dark background. white title. etc.) I will have to see if things improve in time.
Has anyone else had or is having success with ads that clash?