Figure 1: Newton's color circle and spectral inversion. Colors are arranged along the perimeter of a color circle, as indicated by the names on the outside of the circle. Black dots correspond to unique colors (red, green, blue, and yellow) which look subjectively pure. The dashed diameter indicates the axis of reflection corresponding to literal spectral inversion, and the dashed arrows indicate corresponding experiences under this transformation. Letters in parentheses inside the circle indicate the color experiences a spectrally inverted individual would have to the same physical stimuli a normal individual would experience as the colors indicated on the outside of the circle.