In my opinion, if it is a fiberglass part and you can see fibrous material of a different co;or where the finish is coming off, then that would be gelcoat. Gelcoat is the very top finish layer of a fiberglass part. If there is no color change where the finish is coming off then at some point clear coat has been sprayed on the part and that is whats coming off. Gelcoat generally has the color mixed into it when sprayed which is why the color comes off with the gelcoat when it chips or peels.
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