Optical Phenomena Part 1 - Iridescence

(The area of optical phenomena may be a bit of a stretch - but I think it will still apply since color is the overall affect.)

Iridescence:

Iridescence is an optical phenomenon where the hue of a certain material changes depending on the angle of the viewer. It is caused by a surface with multiple layers that cause a phase shift in the light that is reflected away from the material. This is amplified by other light which cannot penetrate the surface at all, causing a change in color depending on distance and angle. Some examples of materials/animalia that are have this ability are as follows; Soap Bubbles, Blue Morpho Butterflys, Golden Stag Beetles, Pearlescent Paints, and Black Crow Feathers.

At it's basis - Iridescence is based on the multiplication of light rays. Not to be confused with Prisms and Rainbows, which are also optical phenomena, though they they both treat light rays and waves differently to create their effect. (more on those two later.)