Are dogs really colour-blind?

Many people think that dogs are colour-blind, but that isn’t true, at least not entirely. Although dogs aren’t completely colour-blind, they do see the world differently from humans. We humans have three types of colour receptors in our eyes. You can think of colour receptors as cones. Dogs only have two of these, so their colour vision is more limited.

How did they discover that dogs aren’t colour-blind?

Scientists have discovered that dogs are not completely colour-blind through experiments testing colour vision. Dogs can therefore still see certain colours. Researchers trained dogs to recognise and select objects based on colour. In doing so, they found that dogs could consistently tell blue from yellow, but struggled with red and green [1]. By measuring how cells in the retina respond to different wavelengths of light, scientists worked out which colours dogs can see, tracing it to two cone types tuned to blue-violet and yellowish-green light [2].

Colours that dogs can indeed see

So dogs are not colour-blind. They simply see colours differently. With two colour receptors instead of three, their spectrum runs mainly to blue, violet and yellow. Red looks somewhat yellowish to them, green barely registers at all, and purple reads as grey.

Humans can distinguish between seven and ten million different colours, more than we even have names for. Dogs work with a much smaller palette: blues, yellows, and a range of greys running from cream through to black and white. What they lack in colour range, they make up for in movement detection.

• Blue: appears blue, much as we see it.
• Yellow: appears yellow, much as we see it.
• Red: probably reads as dark grey or brown.
• Green: also comes through as a greyish shade.

Which colours can’t a dog see?

Due to the limited number of cones in their eyes, dogs cannot see red and green the way we do. Instead, both colours collapse into similar shades of yellow or grey. Blue and purple, by contrast, come through clearly.

What do dogs see that we cannot?

Beyond colour, dogs have a real edge in the dark: much better night vision than humans, thanks to the tapetum lucidum [3]. This light-reflecting layer of cells sits directly behind, or sometimes within, the retina, bouncing available light back through the photoreceptors for a second pass. It’s also part of why movement and shapes stand out more clearly to a dog after sunset than they do to us.

How does colour blindness affect behaviour?

Colour also shapes how dogs interact with their toys. Blue and yellow toys stand out far more than red or green ones, so dogs tend to gravitate toward them without any training at all. Research backs this up: colour cues turn out to be more informative to dogs than brightness alone, at least under normal daylight conditions [4].

The same logic applies to training. Pick colours your dog can see clearly, and cues land faster.

Why have dogs developed a more limited colour vision?

This more limited colour vision wasn’t a disadvantage. Dogs evolved mainly as twilight hunters, and rather than colour, their vision is optimised for movement and contrast, which helps them spot prey more effectively in low light [3]. They also have far more rods (the light-sensitive cells that pick up brightness rather than colour) packed into their retinas than we do, which is part of why dogs see better than humans once the sun goes down.

Are there any glasses or technologies that can help dogs with their vision?

There are a few technologies and aids that can improve or adapt dogs’ vision, although they do not have the same effect as glasses for colour blindness in humans. Here are a few examples:

1. Doggles (Dog Glasses)
   • These are special sunglasses for dogs that offer protection against bright sunlight, UV rays and wind. They are particularly useful for working dogs, such as police or rescue dogs, and for dogs with eye problems such as cataracts.
2. Colour-filtering glasses
   • Although there are no glasses that fully correct dogs’ colour vision, experiments are being conducted with glasses that filter out certain wavelengths of light to improve contrast. This can help dogs distinguish between certain colours or objects.
3. Night vision technology
   • Dogs already see well in the dark, but some researchers have experimented with infrared cameras or glasses that let dogs see even better in complete darkness.
4. Bionic eyes
   • Research is being conducted into bionic implants for dogs with serious eye conditions such as cataracts or blindness. These technologies are still in the experimental phase.

Do dogs have better night vision than humans?

Yes. Dogs see much better in the dark than humans, thanks to a number of evolutionary adaptations [3]:

• Tapetum lucidum: a reflective layer behind the retina that bounces light back through it. This helps dogs see better in low light and gives their eyes that characteristic glow in the dark.
• More rods in the retina: rods are light-sensitive cells that aid vision in dark conditions. Dogs have more of them than humans, which helps them navigate better in low light.
• Larger pupils: dogs can dilate their pupils further than humans, letting in more light and helping them make out objects in the dark.

Thanks to these characteristics, dogs can see much better than we can at night and at dusk. This is particularly useful for their hunting instincts and sense of direction.

What does this mean for dog owners?

When choosing toys or training equipment for your dog, bear their colour vision in mind. Blue and yellow toys stand out the most, whilst red and green objects tend to appear greyish and are harder to distinguish.

Your dog also has an advantage on night-time walks: whilst you struggle to see objects, your dog can orientate themselves perfectly well. This is thanks to their excellent night vision and feel for movement.

Conclusion: are dogs colour-blind?

Although dogs don’t see the world in the full colour palette that humans do, that doesn’t make them colour-blind. Their range is narrower, but they read blue and yellow particularly well, and what they give up in colour, they make up for with sharp night vision and a strong eye for movement. That combination is why the right-coloured toy gets picked first, why a well-chosen training cue lands faster, and why your dog can still find its way round the garden after dark.