The twice I've painted calipers off the car.
First time, my dad's neighbor removed the rear calipers, I painted them, we re-installed them, and sure enough, like said by Ryan, they leaked a few weeks later.
The second time was when I replaced the calipers totally.
If you want to paint calipers, remove the caliper from the rotor, remove bracket from car, put newspaper over the rotor, place caliper on top of the newspaper. put newspaper behind the caliper, and paint away
