colour of law vs color of law

colour of law and color of law both are nouns.

Word	Noun	Adjective	Verb	Adverb
colour of law	Yes	No	No	No
color of law	Yes	No	No	No

As nouns, colour of law and color of law are synonyms defined as:

colour of law and color of law: a mere semblance of legal right; something done with the apparent authority of law but actually in contravention of law

colour of law (noun)	color of law (noun)
a mere semblance of legal right; something done with the apparent authority of law but actually in contravention of law	a mere semblance of legal right; something done with the apparent authority of law but actually in contravention of law