retinal purple vs visual purple

retinal purple and visual purple both are nouns.

Word	Noun	Adjective	Verb	Adverb
retinal purple	Yes	No	No	No
visual purple	Yes	No	No	No

As nouns, retinal purple and visual purple are synonyms defined as:

retinal purple and visual purple: a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light

Other synonyms of retinal purple include rhodopsin.

retinal purple (noun)	visual purple (noun)
a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light	a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light