brown-purple vs brownish-purple

brown-purple and brownish-purple both are adjectives.

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

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

brown-purple (adjective)	brownish-purple (adjective)
of dark purple tinted with brown	of dark purple tinted with brown