Some studies have demonstrated that horses may be able to differentiate shades of yellow and green but not red and blue. Others have indicated that horses see blue and may be able to distinguish between a color and gray of equal brightness. However, most conclude that horses do not perceive color. Binocular Vision 'The horse sees with binocular vision when it uses both eyes to observe an object. The horse's binocular vision, however, is not as good as its monocular vision.
Some horses have better binocular vision because their eyes are set closer together.
Horses often have to learn to use binocular vision through training. Examples are when teaching a rope horse to follow cattle at the correct distance, teaching a barrel horse to judge the distance to a barrel in order to make a turn, or teaching a hunter or jumper the correct approach to a fence. There is not much known about the horse's sense of smell. However, it is generally agreed that it is somewhat well- developed. Horses have apparently learned to associate certain odors with specific conditions considered to be friendly or life threatening.