Dude spray painting someone's car is just over doing it, usually i never touch cars when I'm out being young and rebellious, but on the rare occasion that i do tamper with a car its harmless stuff and done to the cars of people i know very well and won't get ticked off at me. Like wrapping saran wrap around the car or covering it with streamers or filling the inside of the car with packing peanuts. 
I would have beat the hell out of them with my shoe if I caught them.