charcoal grey vs oxford grey

charcoal grey and oxford grey both are nouns.

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

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

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

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