you could use a black leather shoe dye rub that in a leave, get some strong stuff out there instead of ordering expensive leather dyes, that will bring the black back. leather is sprayed with a colour at the factory after time you wear that off and eventually you pick up the hides colour some nasty brown. leather wipes put some moisture back into the leather.
I dyed a momo steering wheel and flogged it off on the internet, the bloke who bought it said it was a top nick black steering wheel, i dont think he realised it was a brown steering wheel to start with.