What colours can cats see? Not black and white, but not like you either
Mostly blues and greenish yellows. Cats do not see in black and white, but they see fewer colours than we do and confuse reds and oranges with greens or greys, much as a person with red-green colour blindness would.
The black-and-white myth
For a long time people repeated that cats, like dogs, saw in black and white. It is not true. Behavioural studies, in which cats are trained to choose between colours of equal brightness, and analysis of their retina both show that they do tell colours apart. The catch is that their colour vision is poorer than ours and that, for them, colour is secondary information: they care far more about movement, shape and contrast. A cat can learn to tell colours apart in an experiment, but in everyday life it rarely uses them to decide anything.
Two types of cone instead of three
Cones are the cells in the retina that make colour vision possible. People with normal sight have three types, sensitive to short, medium and long wavelengths, and by combining their signals we see the whole spectrum of the rainbow. Cats have mainly two types: one sensitive to blues and another to yellowish greens. This is known as dichromatic vision. Some studies have found hints of a third type of cone in very small numbers, but its role is unclear and, in practice, a cat’s colour vision resembles that of a person with red-green colour blindness. They also have far fewer cones than we do, because their retina is dominated by rods, which work in low light and do not see colour.
Which colours it sees well and which it confuses
With those two cones, a cat distinguishes the range of blues and violets and the range of yellows and yellowish greens well. What it cannot do is separate reds from greens: a red toy on the lawn probably looks much like the background to it, dull and greyish. Oranges and browns also blur into yellows or greens. On top of that, even the colours it does see look less saturated, like a faded photo. Its world is not grey, but it is a good deal paler than ours.
What about ultraviolet?
In 2014, a study by Ronald Douglas and Glen Jeffery published in the journal Proceedings of the Royal Society B analysed how transparent the lens is in many mammals and found that in cats and dogs it lets through some of the ultraviolet light that ours blocks. That suggests they might perceive a little ultraviolet, which would let them see, for example, traces of urine or certain patterns that are invisible to us. It is an intriguing possibility, but caution is needed: light reaching the retina does not prove how a cat’s brain interprets it. For now it is a reasonable hypothesis, not a proven fact.
How we know what a cat sees
Nobody can look out from behind a cat’s eyes, so what we know comes from three kinds of evidence. The first is anatomy: counting and classifying the cells in its retina and measuring which wavelengths each type of cone responds to. The second is electrophysiology, recording the retina’s electrical response to lights of different colours, rather like an ECG for the eye. And the third, and hardest, is behavioural testing: teaching a cat to choose a colour to earn food, with the brightness matched so that it cannot simply go by how bright something looks. Behavioural experiments in the mid twentieth century showed that cats can learn to tell colours apart, but that they need a huge number of attempts, which confirms that colour matters little to them.
Why it does not need more colour
For a twilight hunter, seeing lots of colour does not pay. At dawn and dusk, when it hunts, light is scarce and colour barely registers; what puts food on the table is spotting a tiny movement in the grass. So its eye has invested in sensitivity to low light, with plenty of rods and the tapetum lucidum, and in detecting movement, rather than in cones. It is a trade-off: we see vivid colours and fine detail in bright light; the cat sees shapes and movement when we can barely see anything at all.
Choosing toys your cat can see better
If you want a toy to stand out for your cat, think about contrast and movement, not about the colour you happen to like. Blue or yellow toys on a floor of a different shade are easier to see than red ones, which can melt into the background. Feathers, ribbons and fabric mice that move in jerks, stop and start again mimic prey and fire a cat up far more than a shiny ball lying still. And the laser pointer, which it sees because of its movement and brightness, is best used sparingly and always rounded off with a toy it can actually catch, so the hunt is not left unfinished.
When it seems to see worse
If a cat that used to get around easily starts hesitating before jumping, bumping into things or ignoring the toys you show it, this has nothing to do with colour: it may be losing its sight. In older cats this is often down to high blood pressure, and some breeds have inherited retinal diseases, such as the progressive retinal atrophy described in the Abyssinian and the Somali. Cataracts, uveitis or corneal injuries are also worth considering if the eye looks cloudy, red or watery. Any change in the way your cat sees the world calls for an eye check at the vet.
Cats see colour, but only a few colours and muted ones: they distinguish blues and greenish yellows well and confuse red and orange with greens or greys, like a person with red-green colour blindness. Movement and contrast matter far more to them than colour, so choose toys that move and stand out against the floor.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.