Pleochroma

pleochroism – Greek “many colored”, an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90 degree angle to each other. As the divided light follows different paths within the stone and is traveling at different speeds, it may have the result of differential selective absorption. Thus when it leaves the crystal it may have different colors, and thereby makes the stone seem to be of different colors. -Wikipedia online enclycopedia

Alternatively, the piece can be performed with a video accompaniment.