The guy that invents a cost effective repair for scope ring marks and scratches will get very rich. Anyway, I have used Sharpies as well as everything else mentioned. Some match, some glop, some aren't even close and make the fix look worse. One thing I've used that is a good color match, is durable and fairly easy to keep from glopping is the black pens that you use to mark permanent numbers on plastic cattle eartags. Any feed store that sells eartags should have one.
