dark bread vs whole wheat bread

dark bread and whole wheat bread both are nouns.

Word	Noun	Adjective	Verb	Adverb
dark bread	Yes	No	No	No
whole wheat bread	Yes	No	No	No

As nouns, dark bread and whole wheat bread are synonyms defined as:

Other synonyms of dark bread include brown bread, whole meal bread.

dark bread (noun)	whole wheat bread (noun)
bread made with whole wheat flour	bread made with whole wheat flour