chromatic colour vs chromatic color

chromatic colour and chromatic color both are nouns.

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

As nouns, chromatic colour and chromatic color are synonyms defined as:

Other synonyms of chromatic colour include spectral color, spectral colour.

chromatic colour (noun)	chromatic color (noun)
a color that has hue	a color that has hue