it wouldnt make sense to me to change the colors to green as imo camo doesnt help much. I can see a green tank just as well as a yellow one, except maybe from the air, but from the air we get those nice red icons.
also, yellow/red/brown paint on tanks isnt the worst idea. if anyone has ever been out it deep woods you noice that the green,i.e. bushes trees is more common high off the ground, whereas yellows and browns show more on the ground from dead foliage and tree trunks. re/yellow/ brown paint would blend some here and work well with breaking up the vehicles profile, which is the primary reason for camo. I cant say this worked in europe as I've never been there and dont know what the woodland areas are like there.