I used VHT Pontiac Blue Engine Enamel SP122, (from UK Amazon a couple of years ago but now no longer stocked) mainly because it was a shade that almost matched the body colour of the car.
Most of the time the calipers don’t get all that hot, merely boiling in extremis of high speed panic braking! More to the point, once cured (through time and/or heat), the engine enamel is resistant to most solvents including brake fluid.
The disadvantage of this stuff is that several thin coats have to be applied, next one soon after the previous coat is touch dry ~ 10mins in warm dry garage. Fortunately I had a week when not using the car so didn’t need to cook them at a very high temperature, just a few hours with the fan heater to get the chemistry started, and could leave them on the car with fluid etc in them.