Quick backstory - when I ordered my M4 back in late 2016, the factory option black 666 wheels were not available yet. I've always loved the Competition 666 wheels, but always thought that they would look better in black.
Well, now I know that they do look better in black, satin black, to be specific.
If you're in the LA area, the work was done by Kings Powdercoating. I highly recommend them. The results are perfect and the service is excellent. Ask for Jay.