If you set the link color to "black" it will also turn the big Adsense text ad arrow black.
Or blue. Or any color. The arrow is very prominent and a fixture of the text ads.
I had heard BLACK is the best "color" to use, so I've done that, but I've noticed since doing my CTR continues to decline on my main site. Not sure if the issue is related.
The most common color, of course, is BLUE, because that is the default. I personally don't really like it. GREEN is also common.
I'm wondering what the consensus is on this?
I think BLACK looks the most professional/clean, but I'm not sure it works as well -- because it's not as apparent that the ad represents a LINK.
* Note: I just switched back to the Google default on all my text ads. I'll update if there is any change.