Google has updated its AdSense policies which have only gotten more sterner for the publishers. Publishers will get affected a lot by this change.
Earlier publishers could run AdSense and Yahoo! Publisher Network on a 50/50 ad rotation basis. But now the publishers will not be able to run AdSense and YPN on 50/50 rotation if they are using same or very same color palettes. Also using same color palettes for running AdSense on one part and YPN on the other part of the site will be violation of the rules. The ad units that imitate AdSense and are not contextual based will be affected by the change. The ad units cannot have text ads or affiliate links that imitate AdSense. Google's reasonning is:
In order to prevent user confusion, we do not permit Google ads or search boxes to be published on websites that also contain other ads or services formatted to use the same layout and colors as the Google ads or search boxes on that site. Although you may sell ads directly on your site, it is your responsibility to ensure these ads cannot be confused with Google ads.
If the publishers do not want to violate the new rules of Google they have to make some big changes. All those who are rotating AdSense are YPN with border less ads are required to have a colored background on any of the service so that it is known that two ad programs are different. The color scheme of the two can't match with each other.