Because you are making yours removable, you have quite a few options. If carpeted, you could take the boards out, and store them in the garage. That way, they will dry out nicely, and also would be out of the elements except when fishing. If you don't want to go that route, I would use a good oil based paint, and forgo the water sealer. Oil based paint is pretty water resistant in and of itself, and if you store the boards inside, the regular plywood unpainted will last you 15 or more years. If there is any piece of the boat that is the same green color, and removable, you can take that into a paint store and they can match it. Or, an email to Alumacraft may give you the correct color name. May want to mix some sand in with the coat topsides of the deck, for traction.