Why is one red and one yellow?
I'd start by clamping them in a vice by the bolt holes and attacking the old paint with a wire brush attachment on a power drill
Then sand to a smoother finish and paint with high temp caliper paint of your choice.
In terms of their function, if they're old and have sticky pistons then strip them down, get a new seal kit and rebuild. If the pistons are ok then clean them up and reuse otherwise replace them as well.
Or... send them to Godspeed, who'll do a much better job and give you a mint looking set back in return for some £££
