I’ve seen one that was painted and the paint was flaking off. I would think it was from contact and the flexing of the plastic that pops the paint off. I also do not think the material that great for paint being a LDPE. I believe that is the correct material.
I started a vinyl/striker wrap thread. It’s starting to get there with information. I think you’re better off with a wrap than paint.
https://forums.kartpulse.com/t/vinyl-wrap-and-stickers/1980/5