charcoal-grey vs charcoal-gray

charcoal-grey and charcoal-gray both are adjectives.

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

As adjectives, charcoal-grey and charcoal-gray are synonyms defined as:

Other synonyms of charcoal-grey include charcoal.

charcoal-grey (adjective)	charcoal-gray (adjective)
of a very dark grey	of a very dark grey