purple vs regal

purple is a noun but regal is not a noun.

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

As adjectives, purple and regal are synonyms defined as:

Other synonyms of purple include imperial, majestic, royal.

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

purple (verb)	regal (verb)
color purple
become purple