The Collaborative International Dictionary of English v.0.48:

Redness \Red"ness\, n. [AS. re['a]dness. See Red.]
   The quality or state of being red; red color.
   [1913 Webster] Redolence

WordNet (r) 3.0 (2006):

redness
    n 1: a response of body tissues to injury or irritation;
         characterized by pain and swelling and redness and heat
         [syn: inflammation, redness, rubor]
    2: red color or pigment; the chromatic color resembling the hue
       of blood [syn: red, redness]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "redness":
   amblyopia, blearedness, bleariness, bloom, blurredness, blush,
   dim eyes, dim-sightedness, dull-sightedness, fieriness, flush,
   glow, gravel-blindness, hectic, hectic flush, incandescence,
   lippitude, purblindness, rosiness, sand-blindness, whiteness