Source : Webster's Revised Unabridged Dictionary (1913)

Chromatism \Chro"ma*tism\, n. [Gr. ? a coloring.]
   1. (Optics) The state of being colored, as in the case of
      images formed by a lens.

   2. (Bot.) An abnormal coloring of plants.

Source : WordNet®

chromatism
     n 1: hallucinatory perception of colored lights
     2: abnormal pigmentation