The hubs and brake discs on our Corvettes are steel and cast iron, which if left untreated will rust quickly.
It has been my experience that the factory paint applied to the disc is usually of poor quality and thickness, so I like to put a more substantial coat of paint on these surfaces, and the best time to do this is when they are brand new.
The hubs I've found are bare steel, and water will find a way to them and they will start rusting. Although, they are not visible, I still like to keep them rust free.
The proper way to paint the hubs and rotors would be to remove the caliper, the rotor retaining screw, then the rotor.
Wash down all the parts with lacquer thinner or some other solvent that will dissolve any grease.
Lightly spray the hub with something like Rustoleum primer, shielding and masking the surrounding areas. Most solvents will remove overspray before the paint has a chance to dry.
On my new C7 I didn't feel like removing the rotors, so I carefully painted everything with a small brush.
The outside edge of the rotor is prone to rusting. so this got painted too.
Front wheels are easy as you can rotate the disc by hand as you paint.
The rears require the automatic transmission to be in neutral, and when I did that and turned off the engine, all the lights stayed on. Not wanting to be rushed before the battery died, I painted half the rotor, then started the engine, put it in neutral, and rotated the rotor half a turn so I could finish the painting after shutting down the engine. Light will shut off when you are back in Park.
I used an acrylic lacquer because that's what I have in my shop. The hubs come from the factory with a light gray finish, but since my car is Night Race Blue, I thought I would match that by adding black to some dark blue that I had. Paint looked dark enough in the can, but it came out lighter that I wanted it to.
No big deal, next time I feel ambitious, I'll repaint them with a darker blue.
Under normal driving, the rotors should not get hot enough to burn the paint. On the track, this might not work.