I used Metalcast Red for my calipers, cost me around $9 from memory for the can and a lazy sunday afternoon
I already had brake caliper cleaner in my garage, and I used aluminium caliper paint as a primer.
Did this also on my previous R33 and after a clean they come up looking brand new again
3 coats of primer,
I originally tried 2 coats of paint, but it was too bright for my liking, you'll get this deeper kind of red from 4 coats