Just take them off and atack them with a wire brush then spray the disk where it tents to rust with rust converter "To make sure it still doesnt do it under the paint" then spray with brake spray $20 for super shit, and spray away.
If you want a cool colour then you will need to choose wisely.
EG. I wanted mine Gold like the R34, I got gold auto spray and yellow brake spray, Put the brake spray on then let it dry then started on the Gold over the top, I do very heavy breaking in my car and the paint hasnt cracked at all and looks ausome. "When they arnt black lol "