pistachio green vs viridity

pistachio green and viridity both are nouns.

Word	Noun	Adjective	Verb	Adverb
pistachio green	Yes	No	No	No
viridity	Yes	No	No	No

As nouns, viridity is a hypernym of pistachio green; that is, viridity is a word with a broader meaning than pistachio green:

pistachio green: A pale yellow-green colour, like that of the pistachio nut.
viridity: green color or pigment; resembling the color of growing grass

Other hypernyms of pistachio green include green, greenness.

pistachio green (noun)	viridity (noun)
A pale yellow-green colour, like that of the pistachio nut.	green color or pigment; resembling the color of growing grass