Inspired by Jack Storms and his very pretty sculptures which use dichroic crystals, I tried making a simple dichroic crystal shader. The colour you see depends on the angle of the surface.

It uses a little trick for the shadows – when the render sees the material directly, it is glass. When it sees a shadow cast by the material, it sees a transparent material. The node setup is there if you want to have a peek.

If you want to play with coloured shadows in Cycles, you have to tick the Shadows checkbox as indicated by the little note there otherwise all the shadows will render dark. 🙂