Since the boat is some decades old, matching the original paint color is unlikely to work. Even a year of sun and weather can change the color so the boat is no longer the original color.
I was doing some work in the Diamond Paint shop of Delta Marine a couple of years ago. They had a paint rep. trying to match the paint color on a nearly new boat. Eventually they got the insurance company to agree to repaint both sides of the boat – not just do a patch, or even paint one side of the boat.
I was building a fiberglass dodger at the time. I took a cockpit seat locker to Diamond, and they did some paint color matching for the dodger. We agreed on a color that seemed be a pretty good match to the seat locker. Now people walk down the dock and wonder if the dodger was original to the boat, because the color match is pretty good.
On my old boat there was a hull patch that the boat yard would try to color match, but it would only last for 6 months or so before the paint and the nearby gel coat would look different. Because of the location near the bow, I came up with my own solution. I put a big vinyl graphic over it, then matched it with the same graphic on the other side. Now 2 boat owners after me, the latest owner has removed the graphics, and of course the fiberglass under the graphic has been protected from the weather and is a darker / richer color than the rest of the hull. Same issue happens when you change the name of a boat, and remove the old letters – you can see the shadow of the old letters forever afterward. When I had to put a new hailing port on the back of the Tartan, I got the vinyl company to make a big vinyl rectangle to completely cover the original hailing port, and then put the hailing port on the rectangle. You can tell the background color on the decal does not match the hull color, but it is tidy, and centered on the stern. This was a lot less work than repainting the stern .
By the way, if a significant portion of the hull needs painting, I understand vinyl wraps are much less expensive than repainting the entire boat.
Best wishes,
Chris McMuldroch
Tartan 3800
Seattle