Are the colors common nouns

The Word 'color' (or UK colour) is both a verb and a noun.

The noun 'color' is a common noun; a general Word for the property possessed by an object that determines the way the object reflects light; a Word for any color of any kind.

A proper noun is the name of title of a specific person, place or thing; for example, Live Color Nail Enamel or "The Color Purple", a novel by Alice Walker made into a movie in 1985.

Example functions of the Word 'color':

She decided to color her hair for the audition. (verb)

We should paint this room in a lighter color. (noun)