Dogs' perception of colour has been a topic of interest and research for many years. While dogs are not completely colourblind, their colour vision differs from that of humans. This is primarily due to the structure and distribution of their retinal cells, particularly the presence of fewer cone cells specialized for colour vision.

Humans have three types of cones in their retinas, sensitive to different wavelengths of light: red, green, and blue. This enables us to perceive a wide range of colours. In contrast, dogs have two main types of cones, which are most sensitive to blue and yellow wavelengths of light. This means that their colour vision is dichromatic, as they lack the specific cones necessary to perceive the full spectrum of colours humans can see.

Research suggests that dogs' colour vision is similar to that of humans with red-green colour blindness or deuteranopia. They can differentiate between some colours, particularly those in the blue and yellow range, but they have difficulty distinguishing between certain shades of green and red. For example, a red object may appear as a shade of gray or brown to a dog.

It's important to note that while dogs may not have the same colour vision as humans, their visual capabilities excel in other areas, such as motion detection and low-light vision. Dogs have a higher number of rod cells in their retinas, which provide better sensitivity to dim light and motion detection. This is one reason why dogs can be more effective than humans at seeing movement in the dark.

The differences in colour perception between humans and dogs have practical implications. For instance, when designing toys or objects for dogs, considering colour contrast with the background can help ensure they are easily distinguishable. Additionally, training methods for dogs often rely more on visual cues like shape, brightness, and contrast rather than colour-specific cues.

Simply Put:

While dogs do have some degree of colour vision, their perception is limited compared to that of humans. Dogs primarily see the world in shades of blue and yellow, with difficulty distinguishing between certain shades of green and red. Understanding these differences helps us better appreciate the unique visual experiences of our canine companions.

Sources:

• Neitz, J., Geist, T., & Jacobs, G. H. (1989). Color vision in the dog. Visual Neuroscience, 3(2), 119-125.

• Miller, P. E., & Murphy, C. J. (1995). Vision in dogs. Journal of the American Veterinary Medical Association, 207(12), 1623-1634.

• Håstad, O., Victorsson, J., & Odeen, A. (2005). Differences in color vision make passerines less conspicuous in the eyes of their predators. Proceedings of the National Academy of Sciences of the United States of America, 102(18), 6391–6394. https://doi.org/10.1073/pnas.0409228102