brown vs chromatic colour

brown and chromatic colour both are nouns.

Word	Noun	Adjective	Verb	Adverb
brown	Yes	Yes	Yes	No
chromatic colour	Yes	No	No	No

As nouns, chromatic colour is a hypernym of brown; that is, chromatic colour is a word with a broader meaning than brown:

Other hypernyms of brown include chromatic color, spectral color, spectral colour.

brown (noun)	chromatic colour (noun)
an orange of low brightness and saturation	a color that has hue

brown (adjective)	chromatic colour (adjective)
(of skin) deeply suntanned
of a color similar to that of wood or earth

brown (verb)	chromatic colour (verb)
fry in a pan until it changes color
make brown in color