We are all inclined to accept conventional forms or colours as the only correct ones. Children sometimes think that stars must be star-shaped, though naturally they are not. The people who insist that in a picture the sky must be blue, and the grass green, are not very different from these children. They get indignant if they see other colours in a picture, but if we try to forget all we have heard about green grass and blue skies, and look at the world as if we had just arrived from another planet on a voyage of discovery and were seeing it for the first time, we may find that things are apt to have the most surprising colours.
