colour has 21 distinct synonyms spread across 14 of its 14 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
any material used for its color
“she used a different color for the trim”
the timbre of a musical sound
“the recording fails to capture the true color of the original music”
a visual attribute of things that results from the light they emit or transmit or reflect
“a white color is made up of many different wavelengths of light”
an outward or token appearance or form that is deliberately misleading
“he hoped his claims would have a semblance of authenticity”
the appearance of objects (or light sources) described in terms of a person's perception of their hue and lightness (or brightness) and saturation
Synonyms, antonyms and the broader and narrower relations for colour come from Princeton University’s WordNet. Full sources and licences.