trichroism

from WordNet (r) 3.0 (2006)

trichroism
    n 1: pleochroism of a crystal so that it exhibits three
         different colors when viewed from three different
         directions

from The Collaborative International Dictionary of English v.0.48

Trichroism \Tri"chro*ism\, n. [Pref. tri- + Gr. ? color: cf. F.
   trichro["i]sme.] (Min.)
   The quality possessed by some crystals of presenting
   different colors in three different directions.
   [1913 Webster]