Having lost its original color or having an unnatural stain or mark on it.
From Middle English dis- (reversing or undoing) + coloured (having color). The prefix 'dis-' comes from Latin and Old French, combining with the past participle of 'colour' to indicate a reversal of proper coloring.
The spelling 'discoloured' with a 'u' is the British and Commonwealth version, while Americans drop the 'u' — a quirk dating back to Noah Webster's 1828 dictionary reforms that simplified British spellings for American audiences.
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