sepia vs brick red

sepia and brick red both are nouns.

Word	Noun	Adjective	Verb	Adverb
sepia	Yes	No	No	No
brick red	Yes	No	No	No

As nouns, brick red is a hyponym of sepia; that is, brick red is a word with a more specific, narrower meaning than sepia:

Other hyponyms of sepia include copper, copper color, Indian red.

sepia (noun)	brick red (noun)
a shade of brown with a tinge of red	a bright reddish-brown color
rich brown pigment prepared from the ink of cuttlefishes