You know how the head of the skull seemed to blend in with the base? I have seen photos of the whites in Candy Corn blending in with the orange, or the white foam in Drunken blending in. And now the green forehead of the skull bleeding into the blue base - I wonder is this some form of magic? I would think it is hard to do with plastic, isn't it?
I would think just carving until it's thin enough to be transparent (especially when you're going from a light color to a dark color like that, it makes it much easier to get the effect) or just having a very shallow first shot if you're molding. It's definitely difficult to do by hand, but when you've been doing it as long as CC...
Yeah, I think it's like exit said. It's thin enough and there's a good amount of contrast between the two colors. Also, for most of these multicolor skulls, the material used for the skull face usually has some translucency to it (for example, compare the opaqueness of Hardcore White with 3D's slightly translucent white), so the color of the base will be visible through the thin, semi-translucent layer.
It's a really cool effect. For the forehead, the base color bleeds through and accentuates the forehead line. Makes the skulls look more angry.