yellow green vs pea green

yellow green and pea green both are nouns.

Word	Noun	Adjective	Verb	Adverb
yellow green	Yes	No	No	No
pea green	Yes	No	No	No

As nouns, yellow green and pea green are synonyms defined as:

Other synonyms of yellow green include chartreuse, Paris green, yellowish green.

yellow green (noun)	pea green (noun)
a shade of green tinged with yellow	a shade of green tinged with yellow