achromatic colour vs British spelling

achromatic colour and British spelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
achromatic colour	Yes	No	No	No
British spelling	Yes	No	No	No

achromatic colour (noun)	British spelling (noun)
a color lacking hue; white or grey or black	English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')