bluish green vs cyan

bluish green and cyan both are nouns.

Word	Noun	Adjective	Verb	Adverb
bluish green	Yes	Yes	No	No
cyan	Yes	Yes	No	No

As nouns, cyan is a hyponym of bluish green; that is, cyan is a word with a more specific, narrower meaning than bluish green:

bluish green (noun)	cyan (noun)
a blue-green color or pigment	a primary subtractive color for light; has a blue-green color

bluish green (adjective)	cyan (adjective)
of a bluish shade of green	of the blue-green color that is a primary subtractive color of light