Google seems to be broadly testing changing the yellow ad label to a green colored ad label. I am seeing this being reported by my European Twitter folks including @sergey_alakov, @Phil_Blackwell and @MarkWellerSEM amongst others.
Here is a screen shot of the green ad label but there are tons of examples out there:
Here is how it looks with yellow ad label:
Google first began testing the yellow ad label in September 2013. So for them to change the color to green or at least test it, makes a lot of sense.
They need to do something about ad blindness, if anything.
Update: Phil Blackwell sent me a higher resolution version, which is below, click on it to enlarge:
Update 2: Google confirmed they are testing this with a small percentage of searchers.