color wash vs colour wash

color wash and colour wash both are nouns.

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

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

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

color wash (noun)	colour 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