Well, I was watching clips from the old Reach beta, and remembered that the teams were green Spartans and blue, purple, and maroon Elites. And since 343 can change gametype options, they could make Elite and Spartan traits individual. So you could add forced colors for each team. So Spartans can stop being cherry red, and Elites can be their old invasion colors.
343 can do many things, but forcing colours on a team is not one of them, as far as I know Megalo can NOT do this without some sort of power up being picked up.
Green vs Purple is one of the most pointless changes people are suggesting for Reach, it’s easy enough to tell the difference between team mates and enemies considering they are a different race.
However, feel free to post Invasion feedback here: http://halo.xbox.com/Forums/yaf_postst37345_PLAYLIST-FEEDBACK--Invasion.aspx