Nope its just how the person wearing the armour wants it!
If you mean canonically, Halo: Reach messed up a lot armor-wise. The only reason NOBLE team members have different armor permutations is so that the player(s) can more easily tell them apart from one another. According to the Halo novels, all SPARTAN-IIIs were issued MJOLNIR Mk. V and Semi-Powered Infiltration armor in an ochre (olive-green) or grayish-black coloration. Individual SPARTAN-III candidates could not choose the color of their armor. As I said, Halo: Reach messed up everything!
Even with Noble team as one color, or hell, black and white colors, you can still tell them apart, chill out.