Kimkia - 3:52 am on Aug 17, 2012 (gmt 0)
A while ago, I was personally advised by an AdSense rep to remove the borders from ads on my home page and use colors to blend in. I did this. CTR improved; earnings increased. Then I got a warning from them that my AdSense could be terminated because I wasn't following the TOS, and my ads looked too similar to the content. If I remember correctly, I was given a few days to comply, or else.
I forwarded the original email to them, explaining that I was only following their own suggestions. I returned the borders and changed the colors slightly. CTR dropped; earnings decreased. But they told that the original person who had advised me to make these changes no longer worked for Google, and I was ok now that I was in compliance.
So yes, be careful following the advice of AdSense reps; and make sure you keep any communication so you can refer to it later if necessary.