The Collaborative International Dictionary of English v.0.48:
Slate-gray \Slate"-gray`\, a. Of a dark gray, like slate. [1913 Webster]WordNet (r) 3.0 (2006):
slate-gray adj 1: of the color of slate or granite; "the slaty sky of dawn" [syn: slate-grey, slate-gray, slaty-grey, slaty- gray, slaty, slatey, stone-grey, stone-gray]