Get me to In&Out
Sharpie for sure is the answer. As for protection...no ideas other than what you tried. Maybe a few more layers of tape. You could also try black electical tape. Might be a tighter fit and more durable.
While by no means a permanent finish, it is very easy to touch it up.tom_h said:I think auto touchup paint will be better looking & more durable than a sharpie pen, for the cups. The sharpie rapidly fades away when exposed to sun.