Overspray won't hurt the functionality, them tires will work fine. If you want it cleaned for cosmetic purposes, a solvent may work but which solvent will depend on the type of paint and it might attack the rubber. As they say, test in an inconspiciuous area first. Start with acetone and ramp it up from there until it starts damaging the tire. Another option would be to scuff sand, that should clean it off. If all else fails, new wheels aren't expensive.

Dave