charcoal gray vs oxford grey

charcoal gray and oxford grey both are nouns.

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

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

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

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