reddishness vs redness

reddishness and redness both are nouns.

Word	Noun	Adjective	Verb	Adverb
reddishness	Yes	No	No	No
redness	Yes	No	No	No

As nouns, redness is a hypernym of reddishness; that is, redness is a word with a broader meaning than reddishness:

reddishness: The quality of being somewhat red.
redness: red color or pigment; the chromatic color resembling the hue of blood

Other hypernyms of reddishness include red.

reddishness (noun)	redness (noun)
The quality of being somewhat red.	red color or pigment; the chromatic color resembling the hue of blood
	a response of body tissues to injury or irritation; characterized by pain and swelling and redness and heat