Someone named OptiRex, in WebMasterWorld forum, mentioned in this thread that his AdSense earning is greatly increased after he changed the URL link color to blue. He changed it because couple weeks ago, he overheard a conversation between a couple of Joe Public surfers, and one of them say “Click on the blue underlined link, that’s the one you’re looking for.”

Here’s a quote from his post:

Hmmm, I thought, my sites are what I would describe as completely blended, some would probably say maybe too much, with the Adsense links all the same as the site colours and absolutely NO blue hyperlinks.

So I considered a colour re-design and experiment with specific sites to see what happened. I changed the Leaderboard to a red, black and blue and Adlinks solely to traditional blue hyperlink.

The experiment was very encouraging therefore last weekend I implemented it across 110+ sites and the following have been the improvements for seven full days with more or less the same volume of unique visitors.

Impressions +10.39%
CTR +18.18%
eCPM +34.49%
Earnings +48.52%
EPC +17.04%

mzanzig responsed to the threat that links is supposed to be blue colored and underlined.

Fully agree, links should be blue and underlined. And visited links should be purple, by the way. This is an old optimization guideline for Web usability, and I use it across my site.

Well, if I could get 50% increment in earnings, I don’t mind changing my link color to blue :d