purple vs colour in

purple is a noun but colour in is not a noun.

Word	Noun	Adjective	Verb	Adverb
purple	Yes	Yes	Yes	No
colour in	No	No	Yes	No

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

Other hypernyms of purple include color, color in, colorise, colorize, colour, colourise, colourize.

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

purple (verb)	colour in (verb)
color purple	add color to
become purple