aquamarine vs cobalt blue

aquamarine and cobalt blue both are nouns.

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

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

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

aquamarine (noun)	cobalt 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	greenish-blue pigment consisting essentially of cobalt oxide and alumina