blues vs blue devils

blues and blue devils both are nouns.

Word	Noun	Adjective	Verb	Adverb
blues	Yes	No	No	No
blue devils	Yes	No	No	No

As nouns, blues and blue devils are synonyms defined as:

Other synonyms of blues include megrims, vapors, vapours.

blues (noun)	blue devils (noun)
a type of folksong that originated among Black Americans at the beginning of the 20th century; has a melancholy sound from repeated use of blue notes	a state of depression
a state of depression