Maybe. It depends on the material used and I'd use a nontoxic dye to do it. You do not want to put a painted surface into your ears. If anything, the paint would degrade and flake with constant skin contact. You'd need a dye that penetrates and is nontoxic. Even then, the dye might leach out into your skin. Personally, I'd just live with them. You might want to contact the manufacturer and ask if they can color after the fact.
You might want to ask whoever did them to see if it's possible. Another option could be to ask Sleek Audio. I know they offer artwork for any custom whether theirs or not so you could ask them if they would do that.