gray has 18 distinct synonyms spread across 15 of its 15 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.
a neutral achromatic color midway between white and black
any organization or party whose uniforms or badges are grey
“the Confederate army was a vast grey”
the SI unit of energy absorbed from ionizing radiation; equal to the absorption of one joule of radiation energy by one kilogram of matter; one gray equals 100 rad
English radiobiologist in whose honor the gray (the SI unit of energy for the absorbed dose of radiation) was named (1905-1965)
English poet best known for his elegy written in a country churchyard (1716-1771)
American navigator who twice circumnavigated the globe and who discovered the Columbia River (1755-1806)
showing characteristics of age, especially having grey or white hair
“whose beard with age is hoar”
Synonyms, antonyms and the broader and narrower relations for gray come from Princeton University’s WordNet. Full sources and licences.
used to signify the Confederate forces in the American Civil War (who wore grey uniforms)
“a stalwart grey figure”
intermediate in character or position
“a grey area between clearly legal and strictly illegal”