The Collaborative International Dictionary of English v.0.48:

Achromic \A*chro"mic\, a. [Gr. ? colorless; ? priv. + ? color.]
   Free from color; colorless; as, in (Physiol. Chem.), the
   achromic point of a starch solution acted upon by an
   amylolytic enzyme is the point at which it fails to give any
   color with iodine.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

achromic
    adj 1: having no color [syn: achromic, achromous]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "achromic":
   achromatic, anemic, ashen, ashy, bled white, bloodless, cadaverous,
   chloranemic, colorless, dead, deadly pale, deathly pale, dim,
   dimmed, dingy, discolored, dull, etiolated, exsanguinated,
   exsanguine, exsanguineous, faded, faint, fallow, flat, ghastly,
   gray, haggard, hueless, hypochromic, lackluster, leaden, livid,
   lurid, lusterless, mat, mealy, muddy, neutral, pale, pale as death,
   pale-faced, pallid, pasty, sallow, sickly, tallow-faced, toneless,
   uncolored, wan, washed-out, waxen, weak, whey-faced, white