brown vs colourize

brown is a noun but colourize is not a noun.

Word	Noun	Adjective	Verb	Adverb
brown	Yes	Yes	Yes	No
colourize	No	No	Yes	No

As verbs, colourize is a hypernym of brown; that is, colourize is a word with a broader meaning than brown:

Other hypernyms of brown include color, color in, colorise, colorize, colour, colour in, colourise.

brown (noun)	colourize (noun)
an orange of low brightness and saturation

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

brown (verb)	colourize (verb)
fry in a pan until it changes color	add color to
make brown in color