red flag vs allegory

red flag and allegory both are nouns.

Word	Noun	Adjective	Verb	Adverb
red flag	Yes	No	No	No
allegory	Yes	No	No	No

As nouns, allegory is a hypernym of red flag; that is, allegory is a word with a broader meaning than red flag:

Other hypernyms of red flag include emblem.

red flag (noun)	allegory (noun)
something that irritates or demands immediate action	a short moral story (often with animal characters)
a flag that serves as a warning signal	an expressive style that uses fictional characters and events to describe some subject by suggestive resemblances; an extended metaphor
the emblem of socialist revolution	a visible symbol representing an abstract idea