Now it is difficult to conceive how any man calling himself a painter could impose such a thing on the public, and still more how the public can receive it, as a representation of that sunset purple which invariably extends its influence to the zenith, so that there is no pure blue anywhere, but a purple increasing in purity gradually down to its point of greatest intensity, (about forty-five degrees from the horizon,) and then melting imperceptibly into the gold, the three colors extending their influence over the whole sky; so that throughout the whole sweep of the heaven, there is no one spot where the color is not in an equal state of transition—passing from gold into orange, from that into rose, from that into purple, from that into blue, with absolute equality of change, so that in no place can it be said, "here it changes," and in no place, "here it is unchanging."
— from Modern Painters, Volume 1 (of 5) by John Ruskin