well, the '54 ZB was all yellow. Even the wiring. So I'm thinking that would be the way yours would have been.
But if you want to paint those parts black, it would be o.k. The rebuild shop usually paints the starter and generator that color anyway. I usually leave the old cap on the distruibuitor and replace it after I'm done painting. I don't put the sparkplug wires or wiring harness on until I'm done either.