In this article
  1. Do dogs see in black and white?
  2. A colour-blindness test, rebuilt for dogs
  3. Why the red ball vanishes in the grass
  4. Less detail, better at dusk
  5. Choosing toys and cues your dog can see
  6. When to ask your vet about your dog's eyes

You throw the red ball. It bounces twice and settles in the grass, and from where you stand it could not be more obvious. Your dog runs straight past it, circles back with nose down, and runs past it again while you point and say "there!" to no effect at all.

It is tempting to decide that your dog sees the world in black and white. They do not, and the real answer explains that lost ball much better. Here is what the research shows about how dogs see colour, detail and the dark, and how to choose toys your dog can find.

Do dogs see in black and white?

No. Scientists once thought colour hardly mattered to dogs: early studies of their colour vision concluded that colour cues were unimportant to them in everyday life5. Their eyes tell a different story.

Your retina has three kinds of cone, the cells that sense colour. A dog's has two1. In 1989, researchers in California put three dogs through a series of colour tests and worked out that their two cone pigments are most sensitive to light of about 429 and 555 nanometres6. One is tuned to blue light, the other to the longer wavelengths we see as green and red2.

Two kinds of cone point to two-colour, or dichromatic, vision2, and the 1989 tests fitted that picture6. The arrangement led researchers to suspect that dogs see colour much as people with red-green colour blindness do2. In 2017, a team at the University of Bari in Italy found a way to ask the dogs2.

A colour-blindness test, rebuilt for dogs

If you have had your colour vision checked, you may have met the Ishihara plates: circles of coloured dots with a number hidden among them. On plate 22, people with typical colour vision read 26, while people with deuteranopia, a form of red-green colour blindness, see only the 22.

Dogs cannot read numbers, so the team made the plate move. They built a running-cat animation in the reddish shades that form the 2, and another in the shades that form the 6, each on the plate's green background, and played them on a screen to 16 pet dogs2.

Most of the dogs turned their eyes and heads towards the cat drawn from the 2, and looked alert to it. The cat drawn from the 6 got a much weaker response2. Four men diagnosed with deuteranopia, shown the same animations, saw the first cat and not the second2.

When nine of the dogs watched grey copies of the two cats, they gave them no more attention than the background alone, so it is very unlikely the dogs had been going on brightness2. The team concluded that dog colour vision is dichromatic, resembling human red-green colour blindness2.

Colour still matters to dogs

Seeing fewer colours does not mean ignoring them. In a 2013 study, eight dogs with no previous training learned which of two coloured paper squares marked the box they could open, with a piece of raw meat inside. They worked outdoors in natural daylight, and the two squares differed in both colour and brightness, such as dark yellow against light blue5.

Then the researchers reversed one of those differences, offering light yellow against dark blue, say, so that colour pointed one way and brightness the other. All eight dogs leaned towards colour, and half chose by colour in every one of their test trials5. In daylight, the authors concluded, colour may be the more important clue5. Like much dog vision research, both studies are small1, but they point the same way2.

Why the red ball vanishes in the grass

Now back to the lawn. Researchers describe the hues dogs can see as blue, yellow and grey3. In simulations of dog sight, yellow stays yellow, while red, orange and brown all come out yellowish, and so does green grass3.

How colours probably look to a dog
Colour to usTo a dog, in simulations
RedYellowish
Orange or brownYellowish
Green grass and treesYellowish
YellowYellow
BlueBlue

So a red ball on a lawn is, to your dog, probably a yellowish ball on a yellowish background. The colour difference that makes it leap out at you is barely there for them.

What is left is brightness, and even that is unsettled. One study of three dogs found them about half as good as people at telling shades of grey apart, a much older study of two dogs found them about our equal1, and a 1995 veterinary review thought dogs probably had the edge7. Add eyes that see less fine detail than ours1, and a ball half-hidden in long grass gets harder still.

One caution about "what your dog sees" pictures, the table above included: they are simulations built from what is known about dog eyes1, 3, and nobody has yet confirmed how closely they match what dogs actually see1. Read them as the science's best guess.

Less detail, better at dusk

A dog's eye is better adapted to low light than ours. Its retina is mostly rods, the cells that work in dim conditions, and only about 3% of its light-sensing cells are cones, against roughly 5% of ours1. Dogs also have a reflective layer we lack, the tapetum lucidum, which sends light back through the retina a second time. That boosts sensitivity in dim light, but the extra scattering costs some sharpness1.

A 1995 veterinary review judged that dogs probably beat us in dim light, in field of view and perhaps at spotting movement, while falling behind on colour and fine detail7.

How far behind on detail? In a 2017 study in Sweden, dogs and people were tested on cards printed with ever finer stripes; after two pugs and one person who performed poorly were left out, the results came from six dogs (four whippets, a pug and a Shetland sheepdog), five of them in dim light, and seven people8. Some of the dogs saw finer detail than earlier studies would have predicted, yet people could still make out detail from roughly three times the distance, in bright light and in dim light alike8.

So being better at dusk is about catching light, and perhaps movement. It does not mean seeing fine detail in the gloom8. The dogs also varied a great deal, and the pug saw finer detail than the whippets, but with so few dogs the authors could not draw conclusions about breeds8.

Dog eyes in numbers

  • 2kinds of colour cone in a dog's eye, against three in yours1
  • 3%of the light-sensing cells in a dog's retina are cones, against about 5% in yours1
  • About a thirdof the distance: how close a dog must come to see detail a person can just make out, by one study's estimate8

Choosing toys and cues your dog can see

Illustration: a dog peering happily into a pet shop window full of toys and treats

Put together, the research points to some easy changes, whether you are restocking the toy box or choosing a present.

Toys and training kit

Do

  • Choose blue toys for games on grass, which probably looks yellowish to a dog3
  • Let your dog watch the throw: dogs may be better than us at spotting movement, though worse at fine detail7
  • Use blue and yellow if you teach your dog to pick between coloured objects5, 3

Don’t

  • Ask your dog to tell red from green; to them the two can look alike2
  • Mistake a missed ball for stubbornness: the ball you can see may barely stand out to them3

We could find no study that timed dogs searching for blue balls against red ones on a lawn, so the blue rule is a sensible reading of the colour research that nobody has yet put to the test. If your dog's sight is failing, play to their other senses: the PDSA suggests balls with a bell inside and toys stuffed with treats they can sniff out4.

Does your dog have a favourite colour?

Possibly yellow. Researchers in India offered 134 free-ranging dogs a choice of yellow, blue and grey bowls, and yellow was the clear favourite3. In a follow-up, 47 of 61 dogs went to an empty yellow bowl before a grey one with a piece of raw chicken on it3.

The team could not rule out that yellow won because it stood out most, and whether pet dogs share the taste is not known3. Free-ranging dogs in Morocco showed no preference between yellow and blue, though that study was not designed to test colour3. Buy the yellow toy if you like, but your dog may well have other ideas.

When to ask your vet about your dog's eyes

A dog who loses a red ball in long grass is perfectly normal. A dog who stops finding toys they used to spot with ease is worth a closer look. Sight can fade suddenly or gradually, and gradual loss is easy to miss because dogs adapt so well4. The PDSA suggests watching for these signs4.

Signs your dog's sight may be changing

  • Eyes that look cloudy or milky
  • Walking slowly and cautiously
  • Bumping into people, walls or furniture
  • Not wanting to go out at night, or struggling in dim light
  • Being easily startled or nervous
  • Struggling to find toys, balls or food bowls

Contact your vet if you notice any of these, or any other change in your dog's eyes. Many eye problems are easier to treat when they are caught early4.

So the next time the red ball vanishes, your dog is not being dim. To them it is most likely a yellowish ball on a yellowish lawn. Try a blue one, and let them watch it fly.

Sources and further reading8 sources

The small numbers in the article link to the source behind each fact. Sources open on their own websites.

  1. What do dogs (Canis familiaris) see? A review of vision in dogs and implications for cognition researchPsychonomic Bulletin & Review
  2. Are dogs red–green colour blind?Royal Society Open Science
  3. Ready, set, yellow! color preference of Indian free-ranging dogsAnimal Cognition
  4. Blindness in dogsPDSA
  5. Colour cues proved to be more informative for dogs than brightnessProceedings of the Royal Society B
  6. Color vision in the dogVisual Neuroscience
  7. Vision in dogsJournal of the American Veterinary Medical Association
  8. High visual acuity revealed in dogsPLOS ONE