noun, noun which may take the genitive case particle 'no'
chocolate brown
Refers to the color chocolate brown, used as a noun or with の to modify another noun.
彼女はチョコレート色のコートを着ていた。
She was wearing a chocolate brown coat.
このチョコレート色はとても落ち着く。
This chocolate brown color is very calming.
茶色 is a general brown, while チョコレート色 specifically refers to the darker, richer brown of chocolate.
Compound of チョコレート (chocolate) and 色 (color), directly describing the color of chocolate.