What Colours Can Dogs See?
Dogs see in blue, yellow and grey.
Red, orange, yellow and green are perceived to be one hue (yellow).
Blue and purple are perceived as a second hue (blue).
Cyan and magenta are perceived as a neutral hue (grey).
This is similar to a person suffering from red-green colour blindness (deuteranopia).
Human eyes have three ‘cones’ that detect red, green and blue colour – this means that they can identify red, blue, green and yellow wavelengths created by light entering the eye. Dogs only have two cones (yellow and blue), so they cannot distinguish red and green.
This 'cone sacrifice' frees up space for better vision at dawn and dusk through extra light receptive rods.
Dogs can, however, still distinguish a red ball from a green one if there is a difference in the perceived brightness of the two.