oxford gray vs grayness

oxford gray and grayness both are nouns.

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

As nouns, grayness is a hypernym of oxford gray; that is, grayness is a word with a broader meaning than oxford gray:

Other hypernyms of oxford gray include gray, grey, greyness.

oxford gray (noun)	grayness (noun)
a very dark grey color	a neutral achromatic color midway between white and black