Two tone non-skid is a topic that puts a lot of people to sleep so I'll make it short. Gelcoated boat decks get their exterior color before anything else happens in the deck mold. Gelcoat (the paint color you see) is sprayed into the bare mold. Here the mold surfaces are black.
All Sabre models have both smooth and diamond patterned non-skid in the mold surfaces. In order to create the two tone effect a number of steps need to be taken. Step one is to tape off (as you see here) and cover with plastic, all of the shiney surfaces (i.e. the surfaces without non-skid patterns). Then the gelcoat color for the non-skid is sprayed into the mold. Once that has set up we remove the tape and plastic exposing the shiney surfaces and spray the base color onto the mold. When released, the deck will have the two tone look.
And now you know.