This is practically a crossover technique from painting. At one point I was watching a video of PolymerclayTV that reminded me of the time in art school when we were spending hours trying to create all kinds of layers upon layers to get all these beautiful color combinations.
So I decided to show it to you, as it works great on polymer clay as well. And it's a lot of fun.
Materials needed:
White polymer clay (unbaked)
Acrylic paints - all kinds of colors, but as a basic, yellow, orange, red or hues of blue or hues of green, and a metallic or two