It has become fashionable to paint the brake calpers. This is a part of the whole kit which starts with wider wheels including rims with lots of space between the spokes. Sometimes it goes so far, that also the mudguards are being gradually widened using a special roller-mechanism, with a bit of luck sometimes a respray is not even necessary.
Indeed, this is not our subject here. We'll be removing the brake caliper, which will be explained or shown several times on this page. One should bear in mind, that any work done, to make the brake calipers prettier, will be in vain if there's even the slightest suspicion that the piston tends to get stuck.
You have to face the fact that, at this point, a repairing is pointless. Why? Let's assume that the movement of the calipers is too sluggish. It is then quite easy too screw out the guiding-pins and to lever out the respective bushings. Replace them with lightly greased new pins (using Loctite!) together with new bushings and the problem is solved.
All the other parts can also be repaired without problems. The piston however, does pose one particular problem. It's frictional partner is the (brake) cylinder and that can't be replaced. You can of course, invest in a new caliper, a step, which unfortunately, we must recommend if there is the slightest suspicion that the movement is sluggish.
You could of course, counter by saying that after reassembling the unit, it can be tested, to determine whether the brakes are sluggish or not. Actually, one cannot really test them reliably. Who can guarantee that after further wear and tear, the piston won't reach a point where the trouble free sliding back is prevented? Indeed, would every driver even notice if this was happening?
You will probably argue, that the piston can be pressed out (e.g., using compressed-air) and the cylinder surface can be inspected. I agree with you there, one can have a close look. However, can one then judge the surface? What is normal and what is not? Also, how can the problem be solved, without damaging it even more? I wouldn't allow myself such a judgement and I would not suggest that you do either.
So, before you decorate the brake caliper with expensive paint, make sure that it's piston and cylinder and the one on the opposite side, are in order. The same goes for a simple brake-pad change, even if no optical tuning is to be done. 03/13