Zero way to get them back to black unless you re paint them. My SM7s were black but after a few range sessions they start to fade out. Some people like them some people don't but it's going to happen with any club that isn't Chrome.

What I ended up doing was leaving the clubs in CLR for about 20 min than taking a 1000 grit sandpaper. Remove them black and leaves you with a gun metal looking finish that last longer. Just make sure to not put your ferrule in the CLR.

The only way is to have it recoated. It’s the same coating used on some gun barrels.