A company called fibreglast out of Ohio sells a wide variety of colored gelcoats. They rent a couple of color charts with hundreds of colors. Price of gelcoat is reasonable and can be purchased online.
It seems that it's about the only way to match up colors on Hobies. I use the duratech gloss to thin and then spray the gelcoat. With duratech you can get by without adding wax or you can put wax in the top coat. Of course wax is extra. It all depends on how much of the hull you will be doing. I've been changing the hull color on some white boats leaving the decks white.