A person or substance that colors something; someone who applies color or a pigment that adds color.
From colour (British spelling) + -er (agent suffix indicating one who does something). The -er suffix creates agents from verbs, as in 'teacher' from 'teach' or 'baker' from 'bake.'
In British English, 'colourer' is the traditional term for someone in the textile or printing industry, while Americans typically say 'colorer,' showing how a simple suffix choice can be a marker of English dialect.
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