purplish red vs redness

purplish red and redness both are nouns.

Word	Noun	Adjective	Verb	Adverb
purplish red	Yes	No	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