They make little gel-coat kits that you can blend to match. MFGs, at least with boats usually offer color matched repair kits as well.
Is it true fiberglass and gel coat or Filon?
Never repaired Filon, but guessing hard to match since you'd be sanding smooth and filon has visible fibers in its appearance. If it's gel, then that's a repair that's able to be cosmetically repaired with gelcoat patch. And fairly easy DIY if you're at all familiar with auto body type work.
If it's filon, I'd try to get a bit more creative, depending on the location of the gouge. Something like fill it flat with some bondo and put a decal over it, or maybe you could install an additional "vent" or fake cover plate??
Just spitballing here.