reddish blue vs purple

reddish blue and purple both are nouns.

Word	Noun	Adjective	Verb	Adverb
reddish blue	Yes	No	No	No
purple	Yes	Yes	Yes	No

As nouns, purple is a hypernym of reddish blue; that is, purple is a word with a broader meaning than reddish blue:

Other hypernyms of reddish blue include purpleness.

reddish blue (noun)	purple (noun)
a variable color that lies beyond blue in the spectrum	(Roman Catholic Church) official dress of a cardinal; so named after the Tyrial purple color of the robes
	a color between red and blue
	(in ancient Rome) position of imperial status

reddish blue (adjective)	purple (adjective)
	of a color intermediate between red and blue
	belonging to or befitting a supreme ruler
	excessively elaborate or showily expressed

reddish blue (verb)	purple (verb)
	color purple
	become purple