aquamarine vs greenish blue

aquamarine and greenish blue both are nouns.

Word	Noun	Adjective	Verb	Adverb
aquamarine	Yes	No	No	No
greenish blue	Yes	No	No	No

As nouns, aquamarine and greenish blue are synonyms defined as:

Other synonyms of aquamarine include aqua, cobalt blue, peacock blue, turquoise.

aquamarine (noun)	greenish blue (noun)
a shade of blue tinged with green	a shade of blue tinged with green
a transparent variety of beryl that is blue green in color