Why would they do that? The actual Omega Force and MACO armors both look the same as any other armor in the game - you only get a different look because of the costumes that go with the sets.
I agree that it should be different but don't hold your breath.
... you do know that eva suits already come in several color sets right? Different thing completely than omega/maco. The VR set item just looked the same as the common ones, and it seemed that it would have a color set of its own. All the armored suits have a slight goldish tinge it looks like.