Abstract : How do horses perceive colors? The animals' response can be examined using a simultaneous discrimination paradigm, with two types of stimuli: reflective or projected. Our experimental study aimed at exploring color discrimination in an eco-ethological perspective: the presented stimuli are reflective and recall what horses may see in a meadow. We used a simultaneous discrimination paradigm, S+/S-, that implied conditioned responses with positive rewards. The different colors under interest were tested against a neutral grey. Some of these colors were tested against each other. Two subjects were tested for a total of 945 trials. Only one subject reached the discrimination criterion that was set at least 80% of correct responses over 2 consecutive sessions of 20 trials. Colors "yellow", "deep green" and "brown red" were discriminated from the neutral grey. Colors "yellow" and "red" were discriminated from color "deep green". A "light blue-sky" color was not discriminated from the neutral grey. Our results confirmed the dichromatic feature of color vision in horses, being consistent with anatomical and electrophysiological studies. Nevertheless, results may differ from other experimental studies results' depending on the methods used and the presented stimuli.