You can also try to scrub the grey off the skirts as the cars original paint color is underneath that horrid gray. Apparently BMW painted the skirts the car's actual color than painted over it with Gray. Why, I have no idea--rust maybe?
It's a bit of a paint o get all the gray off but it is possible with good results. Indeed, I was doing it until I decided I liked the black better. I just think it gives my car a bit of pop.