I painted the calipers on my Z4 with G2 manufacturing Brake Caliper paint. It is an epoxy base paint; you have to mix two parts. Four years later they look new with no chips, scratches or stains. I took my calipers off the rotors but did not disconnect the fluid lines. BMW replaced my brakes under the service program with no questions ask.
2015 M235i - Estoril Blue - 6 speed - Black Lather - Cold Weather Package - Premium Package - Harmon/Kardon Premium sound