Hi Martin, yep I have just checked mine now and one of the Hong Kong ones has a definite green tinge to it in places on his hat.
I also noticed a few days ago a telephone smurf with the same thing. I couldn't find it just now but I will try and take pics of them both a little later.
I will have to check my ones tonight too....as I said before it's the Papa Captain where I really noticed this...his buttons have gone green and I originally thought it was a different variation. I will post some pics when I get a chance.