i had my calipers replaced so before the new ones were fitted i painted them ( black), i used a high temp paint, but to be perfectly honest i dont think you need to,( under normal driving conditions that is).
I would recommend an epoxy type paint though as it is more durable or household radiator enamel would be fine.
Painting them on the car wouldnt be too hard, i say this as then you dont have to ***** around bleeding them afterwards, get some axle stands and support the car ,use 4 if you can. by the time you have painted the 4th caliper the first one would be dry. when cleaning use a detergent and a stiff brush or some saftey solvent so you dont knacker the seals!!!
if you are applying the stickers make sure you use a laquer over the top of everything - easier to clean and dtops them from peeling at the jet wash.
[Edited on 21-4-2002 by fluff34567]