In the process of removing color; having the property of removing color (British English).
From decolourise + -ing. The -ing form serves as both a present participle (describing ongoing action) and an adjective when used before nouns.
This '-ing' form is doing double duty in English—it can mean 'the process of removing color' or 'something that removes color,' which shows how English loves to multitask with its word endings to express related ideas efficiently.
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