purplish-red vs redness

purplish-red and redness both are nouns.

Word	Noun	Adjective	Verb	Adverb
purplish-red	Yes	Yes	No	No
redness	Yes	No	No	No

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

purplish-red: a red with a tinge of purple
redness: red color or pigment; the chromatic color resembling the hue of blood

Other hypernyms of purplish-red include red.

purplish-red (noun)	redness (noun)
a red with a tinge of purple	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

purplish-red (adjective)	redness (adjective)
of red tinged with purple