Figure 7: Equivalence classes of color perceivers. The Venn diagrams with solid lines indicate the behaviorally defined equivalence classes of color perceivers who have isomorphic color experiences, but not necessarily equivalent color experiences. Dashed circles indicate the possible existence of three classes of trichromats with color experiences that differ from those of normal trichromats at a subisomorphic level, corresponding to the three symmetries of color space indicated in Figure 3.