One thing about color matching that I read about and also observed when filling a scratch on my hull side (orginal factory gelcoat) is that the fill color should be matched before any sanding (or anything else) is done to the area. But after the sanding/polishing/waxing, you may find that the new gelcoat and the surrounding original hull no longer match. No worries however. This happens because the original hull's surface which is exposed to the sun/elements is likely to have a different shading than the unexposed gelcoat which you'll make newly exposed by the sanding etc. In my case, the original surface was very white. But after sanding and polishing, it became a cream white and the new white repair material was evident in constrast. In a few months, the newly exposed surface weathers back and the repair color (which you got right to begin with?!) will again match. Mine ended up very close ... I have to look hard to notice the repair.
