Get the HIN and check iboats.com the carry Spectrum Gelcoat repair. Or call Spectrum and get the right color for your Boat based on HIN. It will never be an exact match due to aging. Note the gel repair material shelf life is only about for 6 months so use it right away.
Or visit your local fiberglass repair shop who has the expertise to match it up. There are also color mixing charts if you want to try to mix. Andy from boatworks on utube is a great DIY resources. Good luck.