Having had color removed or reduced to a pale or colorless state (American English).
From decolorize + -d (past participle marker). The simple -d suffix is used for regular English verbs that end in 'e', following phonetic economy principles.
Many American English words ending in '-ize' create their past tense simply by adding '-d', which is why 'decolorized' follows exactly the same pattern as thousands of other regular verbs, making English grammar predictable once you learn the rules!
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