Hey Nick
The back and front wheel look different anyway so:
1. The finsih may be different, hence one going and not the other.
2. Powder coating the rear wheel in black shouldn't look out of place.
I don't know about Germany, but there are companies that will do this kind of work for you. Cleaned, polished and re-laquered.
They'll get it looking like new again.
Good luck!
