To examine whether fallow deer, Dama dama, have colour vision, we trained four adult females on a two-choice discrimination task, where a positive chromatic stimulus (green) and a negative achromatic stimulus (grey) had similar brightness. The criterion for learning was set at 80% correct responses. To exclude the possibility that the hinds used small differences in brightness to distinguish between the green and the grey stimulus, we conducted a test that differed from the training situation. A light green positive stimulus combined with a dark grey negative stimulus was alternated with a dark green positive stimulus combined with a light grey negative stimulus on every second trial. The positive green stimuli had different reflectance spectra. After training, each of the four hinds showed over 80% correct responses in the test. These results suggest that fallow deer can use colour vision in a discrimination situation by generalizing over slightly different colours, at least in the range of the green spectrum.