deep brown vs burnt umber

deep brown and burnt umber both are nouns.

Word	Noun	Adjective	Verb	Adverb
deep brown	Yes	No	No	No
burnt umber	Yes	No	No	No

As nouns, deep brown and burnt umber are synonyms defined as:

Other synonyms of deep brown include chocolate, coffee, umber.

deep brown (noun)	burnt umber (noun)
a medium brown to dark-brown color	a medium brown to dark-brown color
	dark brown pigment obtained by heating umber