Pick any color spray paint you like when you're at Home Depot or Walmart... I like "aluminum" for brakes. Grab a can or 2 of semi gloss black while you're at it. Next time you happen to have the wheels off, crack a beer or whatever you like to drink. It's best to do this after a good pressure washing, by the way. Spray the calipers or drums generously with brake cleaner. Mask off anything you don't want paint on if you're feeling professional. Alternatively, you can just stick pieces of cardboard in there blocking the spray. Paint the brake components in multiple light coats. Then, take the semi gloss black and spray around inside the wheelwells and visible components. It makes a big difference. Regular spray paint actually holds up well in my experience. Maybe not if you autocross your car or something, but just fine in SoCal traffic.
2017 Subaru Forester 2014 Toyota Prius V 1969 Ford LTD 2014 Honda CB1100
Hmmm... That foam brush idea sounds good! Dip it into a pint can of rustoleum and go for it. Maybe I'll try that on my Maxima. I haven't painted those calipers yet.
I have used a foam brush to paint my calipers. It works great. You don't have to worry about over spray and can get the paint exactly where you want it. And since it is on your calipers you can't see the brush marks like you would if you painted the body of the car.