Well.. if you want your car done right, I would suggest using 2 or 3 colors as a color scheme that you would use throughout your car. My color scheme is black silver and red. Good color schemes for blue cars are.. blue/gold/silver - blue/yellow - blue/black/white
So if you wanted my opinion, I'd say pick a scheme first, then paint your calipers one of those colors. Good luck
i painted my calipers yellow, but my p5 is also yellow, and i think it looks really good, i've gotten lots of completents from complete strangers saying how nice they look!!