Calipers can be painted in normal 2K topcoat paint, over a thin coat of etch, and a light coat of 2K primer, once painted, and allowed to cure for a day or so, they can be keyed with grey Scotchbrite, decals applied, then 2 light thin coats of 2K lacquer to seal over the decals.. allow to cure for another couple of days before carefully fitting.
Your local body shop should easily be able to sort this for you...
Thom