blue has 46 distinct synonyms spread across 11 of its 16 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.
filled with melancholy and despondency
“gloomy at the thought of what he had to face”
belonging to or characteristic of the nobility or aristocracy
“an aristocratic family”
blue color or pigment; resembling the color of the clear sky in the daytime
“he had eyes of bright blue”
1 of the 16 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for blue.
Synonyms, antonyms and the broader and narrower relations for blue come from Princeton University’s WordNet. Full sources and licences.
blue clothing
“she was wearing blue”
any organization or party whose uniforms or badges are blue
“the Union army was a vast blue”
the sky as viewed during daylight
“he shot an arrow into the blue”
the sodium salt of amobarbital that is used as a barbiturate; used as a sedative and a hypnotic
any of numerous small butterflies of the family Lycaenidae