Color Forcing
From QWiki
Standard Color Forcing
This is represented by "enemycolor" and "teamcolor" settings in ezQuake and FuhQuake clients. Those allow you to use one skin for all enemies and onther single skin for all teammates.
Special Color Forcing
Color Forcing is also a name for the feature that allows you to set different color (or skin) on different players in the game, making the players distinguishable from each other even if their personal "skin" and "color" settings are equal.
This feature is available in Qizmo and ezQuake. It's controlled by FPD.