After consulting a couple books, namely the Luftwaffe Colours series and Luftwaffe at War best I can determine is RLM 66 Schwarzgrau or black green. There may have been different colours used depending on where the planes were at and what period of the war. Long story short; I'm saying RLM 66 or RLM 02 Grau. I'm sure others with more info can help validate or refute my findings. Good luck!