yellowish green vs pea green

yellowish green and pea green both are nouns.

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

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

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

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