Engine enamel works well for caliper paint.
The color called "Cadillac Gold"(older Cadillac block paint) works well and looks like yellow zinc plating.We used to use it on vintage race Porsche stuff. It looked good enough to win the Peter Gregg Award for car preparation in the SVRA Grand Prix 1984 at Road Atlanta. Way better than the "Ginsu-Rollerskate" look that is so popular these days. Once they are painted,since the painted surface is smoother than rough cast, they stay clean without too much fuss.
Regards,
Randy D.

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W.R.Durrance
ASE Master Tech
Mercedes Tech 20 Years
68 250SE
68 SAAB 96 Ice Racer
69 300SEL 6.3
70 300SEL 3.5
81 300TDT