Warhammer 40k: Space Marine
That is in reference to vehicles and what not, each color has it's own meaning - such as blue being lucky, yellow making things explode, and red making things go faster. I don't thing that it was referenced in this game do to the lack of Ork vehicles - the rocket boys where about the extent of it all.
"Green is best"
My vote is for "Die, stoopid Humiez!"