I thought I saw a car on here once where you could see the color name. Under the mar on mine is 21. You can see it. Don't remember if there was an m. I think there was.
I think it would be unlikely anything should be visible unless the grease was so heavy the paint fell off. The mar on my car does look different than the other marks.
I don't know on the plate bracket. Did I show you where gm is wrote on my fender extensions? It and firewall writing is very fancy!