color television vs colour television

color television and colour television both are nouns.

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

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

color television and colour television: a television that transmits images in color

Other synonyms of color television include color television system, color TV, colour television system, colour TV.

color television (noun)	colour television (noun)
a television that transmits images in color	a television that transmits images in color