You could get some paint made up/colour matched if you just want a quick fix to eliminate the black scrapes, that's about the cheapest option you'll find next to vinyl wrapping the top of the sills/scuff plates.
Craig took the words out of my mouth. Over here some bigger accessory shops and dedicated automotive paint shops will match and mix your colour and put it in a spray can. It's not hard to mask up a small section and give it a light spray. I could document what to do, but plenty of videos on youtube I'm sure. 
Yeah guys, I'm aware of the paint mixing and matching. I recently did a repair on rear left wheel arch (it took me a looooooong time to repair the rust). However, after painting and clearcoating those areas, the visible edge where the masking tape was used is really... Visible!
Even after I polish them (which is what I still didn't have the time to do), it will be noticeable.
Having in mind that the damage in my case is a long and really narrow area right on the upper edge of the side skirt, I'd leave it like that. It does bother me, but not as nearly as much as did rusty spots on metal.
BTW, the guy who mixed a paint for me did an OK job.
He has the paint data in his database, but didn't have the physical example card to compare it with the actual paint on the car.
Maybe it was a lucky shot
I hope I'll never do any painting ever again.
