He never mentions how many layers it takes him to build up to a particular level of solid color. Him shoeing mannfreds red skull effect does this and it infuriates me.
Usually two or three. If you need more than that using GW colors you are probably doing something wrong. Those are so full of pigments.
It looks to be an artist's take on a very popular episode of Samurai Jack (obviously drawn in a vastly different style).