spectral colour vs spectral color

spectral colour and spectral color both are nouns.

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

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

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

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