It sound like you got a rubber rub rail since it was in a box not 20’ strips. I have accidentally got a little paint on some of my rubber rub rail when I was doing some tough up work and after it dried it would not just peal off. That being said I would never paint a white one black rub rails RUB and my bet sooner or later you are going to RUB against something that will remove that black paint. If I were you I would learn to Love White or try to sell it on E-Bay.
FellowShip
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My motto: Just for the Grins
