the paint arrived yesterday and I had a chance to fiddle around with different mixes of U.S. light olive drab, very dark olive drab and a red oxide primer (to brown it) and I've come to the conclusion this will be more difficult than I thought
the colour on the left is light drab, right side is half dark, half light, centre top is the original and just to the left is the mix with a bit of red oxide, which looks nice but isn't right. I will have another go tomorrow. i'm going to persevere until I get it right