written text vs black and white

written text and black and white both are nouns.

Word	Noun	Adjective	Verb	Adverb
written text	Yes	No	No	No
black and white	Yes	Yes	No	No

As nouns, black and white is a hypernym of written text; that is, black and white is a word with a broader meaning than written text:

written text: something written, especially copied from one medium to another, as a typewritten version of dictation
black and white: communication by means of written symbols (either printed or handwritten)

Other hypernyms of written text include written communication, written language.

written text (noun)	black and white (noun)
something written, especially copied from one medium to another, as a typewritten version of dictation	a black-and-white photograph or slide
	communication by means of written symbols (either printed or handwritten)

written text (adjective)	black and white (adjective)
	not having or not capable of producing colors