Ross from Paid Insights informed me on Twitter that he is now seeing the ad label from Google AdWords in purple, not the yellow or green colors.
Here are some pictures he sent me:
He is/was seeing the purple color on both desktop and mobile searches in Denver, Colorado .
Google has been recently caught testing the ad label in green a week or so ago. So Google testing purple or other colors is not too far fetched.
Forum discussion at Twitter.