brownish-yellow vs amber

brownish-yellow is not a noun while amber is a noun.

Word	Noun	Adjective	Verb	Adverb
brownish-yellow	No	Yes	No	No
amber	Yes	Yes	No	No

As adjectives, brownish-yellow and amber are synonyms defined as:

Other synonyms of brownish-yellow include yellow-brown.

brownish-yellow (noun)	amber (noun)
	a deep yellow color
	a hard yellowish to brownish translucent fossil resin; used for jewelry

brownish-yellow (adjective)	amber (adjective)
of a medium to dark brownish yellow color	of a medium to dark brownish yellow color