I have seen many debates on this subject over the years and there some points worth considering.
1. ALL soldiers want to live to go home.
2. A person in fear of their life WILL stoop to any level to save said life.
3. Germany used about 10 different shades of green throught the war, Luftwaffe included.
The use of captured or otherwise nonstandard paints (mixed, "borrowed" from Luftwaffe supplies etc) is not only possible but likely. If the Germans used green in Tunisia (I believe they did) than any or all of these colors could fit the bill.