brown vs spectral color

brown and spectral color both are nouns.

Word	Noun	Adjective	Verb	Adverb
brown	Yes	Yes	Yes	No
spectral color	Yes	No	No	No

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

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

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

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

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