This was done along time ago to RAP4 paintball markers. Because they sell paintball markers to the the military and LE they colour coded them so that the real thing would not be useed by accident in training. They also sell a series of "less lethal" markers that use can use a capsaicin II (chilli powder) to subdue an individual.
http://www.rap4.com/paintball/os/fon...ont-c-406.html