Well, I was thinking maybe someone can make a plugin that can change the color of players name plates, you know, the thing above a player that displays they're username. I know this is possible because I have seen it on servers before. One server that has this is McPvP. The IP is mcctf.com which is a capture the flag server, and separates people in red or blue teams. If you notice you can see peoples name plates with Red and Blue dividing players from opposing teams.