colour wash vs color wash

colour wash and color wash both are nouns.

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

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

colour wash and color wash: a wash of whitewash or other water-base paint tinted with a colored pigment

colour wash (noun)	color wash (noun)
a wash of whitewash or other water-base paint tinted with a colored pigment	a wash of whitewash or other water-base paint tinted with a colored pigment