pamphlet vs blue book

pamphlet and blue book both are nouns.

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

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

Other hyponyms of pamphlet include ticket book.

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