greenish blue vs aqua

greenish blue and aqua both are nouns.

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

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

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

greenish blue (noun)	aqua (noun)
a shade of blue tinged with green	a shade of blue tinged with green