On this page, the designer sought to show how two different colors, when placed side by side in an alternating pattern, and in very small, "thin" intervals, can create something of an illusion with the eye, making them appear to be an entirely different color, or the mixture of the two. To show that there were indeed two different colors here, the designer coded this page so that the individual color bars of one of the two colors in the mixture was twice as tall as the other. In this case, the colors mixed together were blue and red, making purple/magenta.
Experimenting With Color
How Much to How Much