'Philistine' works, but I'm already a redneck and a hillbilly, so I figured being a 'cretin' was probably sort of a promotion.
Back to the original topic though...
I'm 90% certain that common paintball paint isn't toxic. I've seen guys get hit in or around the mouth, and they didn't immediately start projectile vomiting or anything.
Personally, I'd be pretty comfortable marking the cats with a paintball gun. I mean, worst-case scenario is what? Dead cat? Big deal. If you aren't comfortable with that though, you might consider a paintball-style grenade. I'm not certain if they still make them or not, but they used to make these cannisters that you could pull a pin out of and throw, and when the timer expired they would spray paint (non-toxic non-permanent paintball paint) over everything within a certain radius. Seems like that way you could mark the cats without actually hitting them with anything.