purple vs discolor

purple is a noun but discolor is not a noun.

Word	Noun	Adjective	Verb	Adverb
purple	Yes	Yes	Yes	No
discolor	No	No	Yes	No

As verbs, discolor is a hypernym of purple; that is, discolor is a word with a broader meaning than purple:

Other hypernyms of purple include color, colour, discolour.

purple (noun)	discolor (noun)
(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

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

purple (verb)	discolor (verb)
color purple	change color, often in an undesired manner
become purple	lose color or turn colorless
	cause to lose or change color