In order to ascertain whether the Bezold—Brücke hue shift is of neural or pigment origin, five observers matched monochromatic spots of light, each with the same luminance, but one darkened by the operation of simultaneous brightness contrast. The occurrence of the hue shift in the contrast-darkened spot provides evidence for a neural locus of the effect. In addition, an extended set of measurements with one observer provides additional support for this hypothesis.
STANLEY COREN and BEVERLEY KEITH, "Bezold—Brücke Effect: Pigment or Neural Locus?," J. Opt. Soc. Am. 60, 559-562 (1970)