my buddy was wearing ATACS pants on the weekend...it's a tough call.
Looking at the guys pre-game brief...I'd have pegged MC as TAN (although you're right and some of it looks pretty green). I think it really depends on the cloth and manufacturer's run of material.
The ATACS...I would have put it "green"...but really more because it was muted/darker than "tan" in comparison. The "background" seemed to be grey...and the "foreground" was greeny/?black?/?brown?...or vice versa.
If I were to look at it on it's own...it'd be on the "green" side.
We didn't split tan/green at this game...it was an ID Friend/Foe type game, so it didn't matter what you were wearing.