sepia vs burnt sienna

sepia and burnt sienna both are nouns.

Word	Noun	Adjective	Verb	Adverb
sepia	Yes	No	No	No
burnt sienna	Yes	No	No	No

As nouns, sepia and burnt sienna are synonyms defined as:

Other synonyms of sepia include mahogany, reddish brown, Venetian red.

sepia (noun)	burnt sienna (noun)
a shade of brown with a tinge of red	a shade of brown with a tinge of red
rich brown pigment prepared from the ink of cuttlefishes	a reddish-brown pigment produced by roasting sienna