brownish vs dark-brown

brownish and dark-brown both are adjectives.

Word	Noun	Adjective	Verb	Adverb
brownish	No	Yes	No	No
dark-brown	No	Yes	No	No

As adjectives, brownish and dark-brown are synonyms defined as:

Other synonyms of brownish include brown, chocolate-brown.

brownish (adjective)	dark-brown (adjective)
of a color similar to that of wood or earth	of a color similar to that of wood or earth