  Suppose we stay with the full range of normal human color experience, and so with the color solid as illustrated in figure 5. The discussion of Locke’s scenario shows that a scenario corresponding to a rotation of the color solid around the lightness axis should be avoided. However, as Palmer points out (1999a, 926), there are three inversion scenarios that at least solve the problem posed by the light and saturated yellows. These three scenarios correspond to, respectively, a reversal of the red-green axis; a reversal of the blue-yellow and black-white axes; and the previous two reversals taken together: a reversal of the red-green, blue-yellow, and black-white axes. These three scenarios are (approximately) illustrated in Figure 6 below.