The Collaborative International Dictionary of English v.0.48:

Discolor \Dis*col"or\, v. t. [imp. & p. p. Discolored; p. pr.
   & vb. n. Discoloring.] [OE. descolouren, OF. descolorer, F.
   d['e]colorer, fr. L. dis- + cololare, coloratum, to color,
   color color. See Color.] [Written also discolour.]
   1. To alter the natural hue or color of; to change to a
      different color; to stain; to tinge; as, a drop of wine
      will discolor water; silver is discolored by sea water.
      [1913 Webster]

   2. To alter the true complexion or appearance of; to put a
      false hue upon.
      [1913 Webster]

            To discolor all your ideas.           --Watts.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

discolour \discolour\ v.
   same as discolor. [Brit.]

   Syn: discolor, colour, change color.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

discolour
    v 1: change color, often in an undesired manner; "The shirts
         discolored" [syn: discolor, discolour, colour,
         color]