aqua vs cobalt blue

aqua and cobalt blue both are nouns.

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

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

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

aqua (noun)	cobalt blue (noun)
a shade of blue tinged with green	a shade of blue tinged with green
	greenish-blue pigment consisting essentially of cobalt oxide and alumina