In Team Instant Action there are two teams (duh) one team is Marines with green army-ish Nanosuits and the other team is C.E.L.L. with blueish Nanosuits. But in regular Instant Action all players are wearing Marines Nanosuits.
My idea is that just like how in "Classic" mode of games Marines and C.E.L.L. have non-nanosuit skins, in Instant Action (when you do have nanosuits) instead of all players "wearing" either C.E.L.L. or Marines suits their nanosuits look like the standard (singleplayer) suit. I think that it would be less confusing and more fun.