dark bread vs brown bread

dark bread and brown bread both are nouns.

Word	Noun	Adjective	Verb	Adverb
dark bread	Yes	No	No	No
brown bread	Yes	No	No	No

As nouns, dark bread and brown bread are synonyms defined as:

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

dark bread (noun)	brown bread (noun)
bread made with whole wheat flour	dark steamed bread made of cornmeal wheat and flour with molasses and soda and milk or water
	bread made with whole wheat flour