Straight out "engine paint" . . .
(I didn't bother to primer. I should have, probably, but I'm not worried about that.)
Why?
I figured engine paint should handle any heat put off by the calipers and disc brakes.
I also COULD have used wheel paint . . .
They didn't have a color in stock I liked and I wanted to get these done.
I wonder how hot they get . . .

(remember-> most center caps and wheel covers are plastics)
So far, it has held up just fine.
Anyways, as there is an RTV glue layer between the cap and rim itself, so it shouldn't be over the heat rating of the engine paint.