Ellsworth Kelly, Blue Green Red, 1962-63. Oil on canvas, 91" x 82."
This picture hangs in the peculiar 20th century collection at the Metropolitan Museum. I love the way it refers so directly to landscape, but remains stubbornly abstract. The colors are virtually identical in value and saturation, and the shallow space is carved out by the fact that red tends to proceed and blues and greens tend to recede (with green receding slightly more than blue).
The scale is is perfect, both in terms of the part-to-whole-relationships, and in terms of the size of the picture in relation to viewer - it's bigger than you, which gives it the grandeur of landscape, but not so large that you can't take it in all at once. And that cigar shape has the strange quality of looking like it's moving very quickly, but at the same time being perfectly still, like those odd stop-time photos you'll sometimes see of a bullet frozen in the air.
The thing I admire so much about Kelly is his clarity. Did you ever have a person, a teacher maybe, explain a very difficult concept to you in one or two deceptively simple sentences, and then suddenly you understood the meaning perfectly? Kelly's work, for me, is the visual equivalent of that particular phenomenon.