Mark Rothko

He is classified as an abstract expressionist, although he himself rejected this label, and even resisted classification as an "abstract painter".

I insist upon the equal existence of the world engendered in the mind and the world engendered by God outside of it. If I have faltered in the use of familiar objects, it is because I refuse to mutilate their appearance for the sake of an action which they are too old to serve, or for which perhaps they had never been intended. I quarrel with surrealists and abstract art only as one quarrels with his father and mother; recognizing the inevitability and function of my roots, but insistent upon my dissent; I, being both they, and an integral completely independent of them.

source wikipedia