blue joke vs joke

blue joke and joke both are nouns.

Word	Noun	Adjective	Verb	Adverb
blue joke	Yes	No	No	No
joke	Yes	No	Yes	No

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

Other hypernyms of blue joke include gag, jape, jest, laugh.

blue joke (noun)	joke (noun)
an indelicate joke	a ludicrous or grotesque act done for fun and amusement
	activity characterized by good humor
	a triviality not to be taken seriously
	a humorous anecdote or remark intended to provoke laughter

blue joke (verb)	joke (verb)
	act in a funny or teasing way
	tell a joke; speak humorously