People are used to #0000FF. The best thing to do is, to integrate it with your design/website (as far as the ToS allows you to). My favourite colour, though, is #FF0099.
I have changed the colors of Adsense at my blog and saw almost no difference at all. I think that Internet users are clever enough to depend on colors much... IMHO
I'd say it depends on the color scheme of the site. I use different colors on different sites, and it's not possible to judge which one is best.
To have a great idea on blending color with your site's text color and what should be the Title Color of your adsense ads you may refer those site which earn lots of money from adsense daily. You have a list of those successful adsense sites just log in to your adsense account and read the success story google placed for the others to copy their success. Just go to those site and have a look on those site adsense title color blending. Is this helpful to you. You can have an idea of proper blending of ads with text of the site in a site in my signature.