greyest

1. of an achromatic color of any lightness intermediate between the extremes of white and blackExamples: "the little grey cells"; "gray flannel suit"; "a man with greyish hair"Synonyms: gray, grayish, grey, greyish

2. showing characteristics of age, especially having grey or white hair; -ColeridgeExamples: "whose beard with age is hoar"; "nodded his hoary head"Synonyms: gray, gray-haired, gray-headed, grey, grey-haired, grey-headed, grizzly, hoar

3. used to signify the Confederate forces in the American Civil War (who wore grey uniforms)Examples: "a stalwart grey figure"Synonyms: gray, grey

4. intermediate in character or positionExamples: "a grey area between clearly legal and strictly illegal"Synonyms: gray, grey