The RKG Blog got official word from Google, which I confirmed, that the pink ads we have been seeing for months now are now official. I personally have been seeing them since last night, and everyone will ultimately see them by the end of this week.
Google told RKG:
Starting today and ramping up to 100% globally by the end of this week, we'll be changing the background color for ads that appear above the search results on Google.com as well as our local domains. The ads, which currently have a pale yellow background, will change to have a pale purple background. This change is part of the "look and feel" update to our color palette and logo that we made back in May of this year to keep the Google results page looking fresh and modern. This is purely an aesthetic change to our ads and won't have any impact on the way we target or serve advertisements on Google.com.
Here is a picture:
Remember, Google switched to yellow backgrounds in April 2007:
Prior to yellow, there were the blue AdWords backgrounds:
AdWords advertisers hope the changes has a positive change to their click through rates.