blue book vs pamphlet

blue book and pamphlet both are nouns.

Word	Noun	Adjective	Verb	Adverb
blue book	Yes	No	No	No
pamphlet	Yes	No	No	No

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

Other hypernyms of blue book include booklet, brochure, folder, leaflet.

blue book (noun)	pamphlet (noun)
a register of persons who are socially prominent	a brief treatise on a subject of interest; published in the form of a booklet
a report published by the British government; bound in blue	a small book usually having a paper cover
a blue booklet used in universities for writing examinations