oxford gray vs oxford grey

oxford gray and oxford grey both are nouns.

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

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

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

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