Is red a noun or a verb?

The Word 'red' is a noun and an adjective.

The noun 'red' is a Word for a color.

The adjective 'red' is a Word that describes a noun as that color.

Examples:

We're painting the patio furniture red. (noun)

You have some red paint on your face. (adjective)

The verb form is to redden (reddens, reddening, reddened).