Oh my, look at all the black paint slowing this car down
Seriously the colors mean little if anything, originally the 930 calipers were anodized black and later painted black as protection from corrosion.
When the switch was made to Brembo, which has 2 lines unsurprisingly referred to as painted and unpainted. They chose the painted line for the same reason.
Later when they started really going crazy(using adequately sized rotors and calipers) they painted the top of the line red. Later they used other colors to delineate cosmetically, one model from another or as an option.
Lately the top of the lines are yellow w/ other colors optional.