I was asked an innocent question about interference- and dispersion like effects in rendering, and I did the following nifty test:
Basically, it's three layered copies of the material. One contains the diffuse component, and the reflection color set to red, and with an anisotropic reflection. The other two has the diffuse component set to black, and have green and blue reflection colors respectively.
The anisotropy is the same but I modified the anisotropy angle slightly between the three. This gives really neat "rainbow effects" like in a CD-Rom surface.
Enjoy the trick.