It changes depending on the level. For that part of that level, they chose green to be the matte color. If you watch carefully as you play, you can see when they change it. It usually happens when you go from above ground to below ground or vice versa.
Yeah, I get the primary colors for my 'shadow'... starts off with Green in the Ghost hideout, then you get Blue a little later on, and I believe Red is in the "Dead City". I didn't think anything of it at first that it's RGB, but now it makes sense ...
This is really annoying, but you get over it, I just keep shaking my head each time I enter a map.
Edit: Re the poser above me, we didn't see any of this in Doom3, people complained the game was overly DARK (black) - I think I'll probably wait for the next id title to go on sale, not to save money, but because by then it will have most of it's 'quarks' figured out. <3 tech 5, <\3 that Rage seems to be a Tech Demo release
