Rothko's work really can't be photographically reproduced. It is almost entirely dependent on color gradations that seep through like pentimento under varying lighting conditions, and the pigments, layering, and multiple levels of color fail entirely in photographic reproduction.
Not to mention the size. Having one of these human-sized images a foot or two from you face is an entirely different experience than 100 x 200 pixels on the computer in your lap (where the color changes if you just move the angle of the screen).
I'm getting a hankering to visit a museum with Rothkos really soon. Wish Houston was a little closer to New England. :)