[1] : The Collaborative International Dictionary of English v.0.48

colorless \col"orless\, a.
   1. without color; not distinguished by any hue; transparent;
      as, colorless water; a colorless gas.

   note: narrower terms: ashen, bloodless, livid, lurid, pale,
         pallid, pasty, wan, waxen; neutral; white also
         see: achromatic, colorless.
         1913 webster + wordnet 1.5

   2. free from any manifestation of partial or peculiar
      sentiment or feeling; not disclosing likes, dislikes,
      prejudice, etc.; as, colorless music; a colorless style;
      definitions should be colorless.
      1913 webster

   3. having lost its normal color.

   note: narrower terms: blanched, etiolate, etiolated,
         whitened; bleached, faded, washed-out, washy;
         dimmed, dulled, grayed; dirty; dull, sober,
         somber, subfusc colored

   syn: colorless, uncolored, uncoloured.
        wordnet 1.5 +pjc
see also:
ashen, bloodless, livid, lurid, pale, pallid, pasty, wan, waxen neutral white achromatic colorless blanched, etiolate, etiolated, whitened 
bleached, faded, washed-out, washy dimmed, dulled, grayed dirty dull, sober, somber, subfusc colored 

[2] : WordNet (r) 2.0

colorless
     adj 1: lacking in variety and interest; "a colorless and
            unimaginative person"; "a colorless description of the
            parade" syn: colourless ant: colorful
     2: weak in color; not colorful syn: colourless ant: colorful
see also:
colourless colorful 

[3] : Moby Thesaurus II by Grady Ward, 1.0

128 moby thesaurus words for "colorless":
   abstract, achromatic, achromic, aloof, anemic, arid, ashen, ashy,
   barren, blah, blanched, bland, blank, bled white, bloodless,
   blurry, boring, cadaverous, characterless, chloranemic, cold, dead,
   deadly pale, deathly pale, detached, dim, dimmed, dingy,
   discolored, disinterested, dismal, dispassionate, doughy, drab,
   draggy, drearisome, dreary, dry, dryasdust, dull, dusty, effete,
   elephantine, empty, etiolated, exsanguinated, exsanguine,
   exsanguineous, fade, faded, faint, fallow, feeble, flat, ghastly,
   gray, haggard, hazy, heavy, ho-hum, hollow, hueless, hypochromic,
   impersonal, inane, inexcitable, insipid, jejune, lackluster,
   leaden, lifeless, livid, low-spirited, lurid, lusterless, mat,
   mealy, milk-and-water, muddy, namby-pamby, neutral, obscure, pale,
   pale as death, pale-faced, pallid, pasty, pedestrian, plodding,
   pointless, poker-faced, poky, ponderous, prosaic, prosy, remote,
   sallow, sickly, slow, solemn, spiritless, sterile, stiff, stodgy,
   stuffy, superficial, tallow-faced, tasteless, tedious, toneless,
   uncolored, unimaginative, uninspired, uninteresting, unlively,
   vacuous, vague, vapid, wan, washed out, washed-out, waxen, weak,
   whey-faced, white, wishy-washy, withdrawn, wooden

Colorless >> C Words
Colorless, definition of term: Colorless
colorless_pag1.html