I guess green probably isn't that high in the 'favourite colour' list of top 10 favourite colours to buy a car.
On that basis I'd wager that green cars on average trade at a lower price than their similar model clones in other more favourable colours.. (certainly always the way with those 'lovely' Tanzanite green mercs from a few years back..
BRG on english sports cars clearly an exception here though I'm sure..