I have used white pigment in epoxy for the hull of my last couple kayaks and it worked out well. I used Systems Three epoxy and I bought the pigment from them also. To get a solid color look I needed to use the maximum amount of pigment that the manufacturer recommended, 10-1. I used the pigment for the saturation coat, applying the fiberglass and the fill coats. With each layer the color became more solid. I found it very helpful to use the pigment when applying the fiberglass because it showed any areas of the cloth that were starved. I applied paint to the exterior of the hull for UV protection and wear. The interior was left just epoxied and it hasn't shown any signs of degradation. Placing a layer of pigmented fiberglass over the deck will give you some scratch depth but also added weight. I guess if you don't mind the added weight and work, adding fiberglass would do the job.