Aside from practicalities of printing, what made me decide not to use color in this book were issues of visual perception. For much as it is easier to read text in black and white, so also it is easier to assimilate detailed pictures if they are just in black and white. And in fact many types of images in this book show quite misleading features in color. In human visual perception the color of something tends to seem different depending on what is around it—so that for example a red element tends to look purple or pink if the elements around it are respectively blue or white. And particularly if there are few colors arranged in ways that are not visually familiar it is typical for this effect to make all sorts of spurious patterns appear.