The Collaborative International Dictionary of English v.0.48:

Polychromatic \Pol`y*chro*mat"ic\, a. [Poly- + chromatic.]
   Showing a variety, or a change, of colors.
   [1913 Webster]

   Polychromatic acid (Old Chem.), a substance obtained by the
      action of nitric acid on aloes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

polychromatic
    adj 1: (of light or other electromagnetic radiation) composed of
           more than one wavelength; "polychromatic light" [ant:
           homochromatic, monochromatic]
    2: having or exhibiting many colors [syn: polychromatic,
       polychrome, polychromic]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "polychromatic":
   bicolor, bicolored, chromatic, cold, colorful, colorific, coloring,
   colory, cool, crazy, daedal, dichromatic, discolor, divers-colored,
   glowing, harlequin, harmonious, kaleidoscopic, many-colored,
   matching, medley, monochromatic, monochrome, monochromic, motley,
   multicolor, multicolored, multicolorous, multihued, parti-color,
   parti-colored, pigmentary, polychrome, polychromic, prismal,
   prismatic, rainbow, shot, shot through, spectral,
   thunder and lightning, tinctorial, tingent, toning, trichromatic,
   trichromic, tricolor, tricolored, two-tone, varicolored,
   variegated, versicolor, versicolored, warm