gelcoat can be like a paint
and sprayed on or gell coat can be inbedded in the fiberglass so scratchs same color. paint
only covers the exterior . and remember paint come in many forms.
best i can say if you scrach it and it same as top in color it is probanly gelcoat. most confuseing . if it chios off in flakes it is probably paint , if it just scratches and leaves white it probably gelcoat top coat
if all your are doing is polishing a fiberglass polish will work on gellcoat and paint .
if you are removeing oxidation i would ask a local marine rv fiberglass body shop type person or try in a hidden area like the roof.