redness vs cherry red

redness and cherry red both are nouns.

Word	Noun	Adjective	Verb	Adverb
redness	Yes	No	No	No
cherry red	Yes	No	No	No

As nouns, cherry red is a hyponym of redness; that is, cherry red is a word with a more specific, narrower meaning than redness:

redness: red color or pigment; the chromatic color resembling the hue of blood
cherry red: a red the color of ripe cherries

redness (noun)	cherry red (noun)
red color or pigment; the chromatic color resembling the hue of blood	a red the color of ripe cherries
a response of body tissues to injury or irritation; characterized by pain and swelling and redness and heat