Do you want it purely black, as in blacked out?
You can do that yourself. Sand the racquet down. Spray some primer. Spray some black spray paint (I recommend Rustoleum, or DupliColor for automotive paint), and you're good to go. Don't rush!!
If you have something like a Pure Drive, and you want only the blue to be black.... I don't know.... Because it's really hard to be super precise with keeping the little details.