To alter or spoil the color of; stain.(verb-transitive)
To become altered or spoiled in color.(verb-intransitive)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "discolor" in a sentence
"'discolor' to the point of losing its effects before the fly is either too beat up to continue using or is now sitting, attached to a rock on the bottom of the stream."
""Stainless" is a misnomer; it should be described as "stain resistant" because it will discolor or oxidize a bit, but I don't clean my stainless rifles and sidearms any differently (or any less thoroughly) than those of blued or Parkerized steel."
"Don't try to skin it yourself ... there is a pretty good chance you will dislodge or discolor feathers if you aren't used to doing it."