I painted my calipers on my old car with 1,500 degree engine paint, and they look perfect after almost a year. Unfortunately, it's a bitch to clean them unless you paint them black.

Before you paint them use something like naval jelly to remove the rust from the caliper so it sort of preps it. Make sure you have all the jelly of, then paint away. I think after about 3 coats it looked so fresh and so clean. Also, remember than you will need to tape of your brake pads, rotors, etc.