Fibersen: Waterproof, yes. Paint/dye proof?

Hey, everyone!
Just finally received my accessories set in the mail this week after 6 months of shipping time (Covid), and finalized the step up to a higher quality shamisen. Got a quick question though.

I want to decorate the skin on my shamisen. Fibersen says it’s waterproof, so I want to know whether or not any paint or dye I would use will hold, or if it will just flake off. I can’t find anything on the material itself, and it’s not really something I’m in the position to “test”.

Does anyone have more info on what the material is made of, or better yet, have any of you added designs or decoration to your fibersen skins?