blue blood vs prince

blue blood and prince both are nouns.

Word	Noun	Adjective	Verb	Adverb
blue blood	Yes	No	No	No
prince	Yes	No	No	No

As nouns, prince is a hyponym of blue blood; that is, prince is a word with a more specific, narrower meaning than blue blood:

blue blood: a member of the aristocracy
prince: a male member of a royal family other than the sovereign (especially the son of a sovereign)

blue blood (noun)	prince (noun)
a member of the aristocracy	a male member of a royal family other than the sovereign (especially the son of a sovereign)