Fig. 3. Hexagon colour space showing contour plots of predicted colour shift, considering von Kries colour constancy and a change in the spectral quality of illumination from a correlated colour temperature of 4800 to 10000K. Numbers on the contours represent the distance a colour in that region of the hexagon would shift for the change in illumination colour. The distance from the centre of the hexagon to each corner is 1 unit. Colour classes are related to the three photoreceptor peaks (Ultraviolet, Blue and Green) of the honeybee. The contours are calculated from 99 theoretical colours described by Dyer (Dyer, 1998) and are plotted in a hexagon colour space after Chittka (Chittka, 1992).