You certainly can stain or dye maple any colour you want and then clear coat it.

If you're talking about just doing the fretboard a different colour than the rest of the neck, I think the difficulty would be not getting bleed from the fretboard wood onto the wood under it. I'm not sure simply masking would be able to prevent that. I've never tried it, so can't say emphatically one way or the other.

FWIW I don't think I'd use any kind of paint on a fretboard though