yellowish brown vs raw sienna

yellowish brown and raw sienna both are nouns.

Word	Noun	Adjective	Verb	Adverb
yellowish brown	Yes	No	No	No
raw sienna	Yes	No	No	No

As nouns, yellowish brown and raw sienna are synonyms defined as:

Other synonyms of yellowish brown include buff, caramel, caramel brown.

yellowish brown (noun)	raw sienna (noun)
a medium to dark tan color	a medium to dark tan color
	a yellowish-brown pigment made from untreated sienna