i am not sure if they do this on all frames but,
on my like 1990 straight jackets the plastic has a coding on it that adds color.
now in their more recent frames i have no clue, my oil rigs look like they are a solid white plastic, same with the fuel cells. my gascans look like they could be coded.
i would not sand them,
Pics man, I can't wait to see what someone black through marriage looks like - [sebastian]