congo red vs azo dye

congo red and azo dye both are nouns.

Word	Noun	Adjective	Verb	Adverb
congo red	Yes	No	No	No
azo dye	Yes	No	No	No

As nouns, azo dye is a hypernym of congo red; that is, azo dye is a word with a broader meaning than congo red:

congo red: a red-brown azo dye especially as a chemical pH indicator (congo red is red in basic and blue in acidic solutions)
azo dye: any dye containing one or more azo groups

Other hypernyms of congo red include acid-base indicator.

congo red (noun)	azo dye (noun)
a red-brown azo dye especially as a chemical pH indicator (congo red is red in basic and blue in acidic solutions)	any dye containing one or more azo groups