umber vs burnt umber

umber and burnt umber both are nouns.

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

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

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

As nouns, burnt umber is a hyponym of umber; that is, burnt umber is a word with a more specific, narrower meaning than umber:

Other hyponyms of umber include raw umber.

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

umber (adjective)	burnt umber (adjective)
of the color of any of various natural brown earth pigments