charcoal grey vs charcoal gray

charcoal grey and charcoal gray both are nouns.

Word	Noun	Adjective	Verb	Adverb
charcoal grey	Yes	No	No	No
charcoal gray	Yes	No	No	No

As nouns, charcoal grey and charcoal gray are synonyms defined as:

Other synonyms of charcoal grey include charcoal, oxford gray, oxford grey.

charcoal grey (noun)	charcoal gray (noun)
a very dark grey color	a very dark grey color