The Collaborative International Dictionary of English v.0.48:

Monochromic \Mon`o*chro"mic\, a.
   Made, or done, with a single color; as, a monochromic
   picture. Called also, monochromatic and monochrome.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

monochromic
    adj 1: having or appearing to have only one color [syn:
           monochromatic, monochrome, monochromic,
           monochromous]