slate-grey vs stone-grey

slate-grey and stone-grey both are adjectives.

Word	Noun	Adjective	Verb	Adverb
slate-grey	No	Yes	No	No
stone-grey	No	Yes	No	No

As adjectives, slate-grey and stone-grey are synonyms defined as:

Other synonyms of slate-grey include slate-gray, slatey, slaty-gray, slaty-grey, slaty, stone-gray.

slate-grey (adjective)	stone-grey (adjective)
of the color of slate or granite	of the color of slate or granite