the Chams option is a button to choose the color you want the program to react to. Enemy Name Tags is the default, and has a checkbox of its own, but if you use colored chams from a hack or colored bodies/whatever from mods you can have it react to those colors instead.
If you're using mods to get the colors then it would be best to only use the Chams option in OMA matches since your team mates will be the same color as your enemies.