Thanks for the visit , yes you are rite in fact all the dark colours , tabahi when taken care properly & looked Bad if wont , she never went to automatic wash but on the other side deposit of salt is not good to rub with micro fibre so the step I took :
Touch less wash
Double bucket wash
Detailing
mashaALLAH your WV-gti is fun to drive 
Thanks Hamza , soon they'll be replaced with the original Alloy