cornflower blue vs blueness

cornflower blue and blueness both are nouns.

Word	Noun	Adjective	Verb	Adverb
cornflower blue	Yes	No	No	No
blueness	Yes	No	No	No

As nouns, blueness is a hypernym of cornflower blue; that is, blueness is a word with a broader meaning than cornflower blue:

cornflower blue: A shade of medium-to-light blue containing relatively little green compared to blue.
blueness: blue color or pigment; resembling the color of the clear sky in the daytime

Other hypernyms of cornflower blue include blue.

cornflower blue (noun)	blueness (noun)
A shade of medium-to-light blue containing relatively little green compared to blue.	blue color or pigment; resembling the color of the clear sky in the daytime