Animal Color Vision, From One to Five Cone Types

How animal colour vision works

Colour vision depends on cone cells in the retina. Each type of cone contains a pigment tuned to a different band of wavelengths, and the brain works out a colour by comparing how strongly each type responds. With one type of cone there is nothing to compare, so the animal sees brightness but not hue. Each extra type adds another dimension of colour.

Animals are usually grouped by how many cone types they have, the same five groups the infographic illustrates:

• Monochromats (one cone type): whales, dolphins, seals and owl monkeys
• Dichromats (two): most mammals, including dogs and cats
• Trichromats (three): humans, apes and Old World monkeys, plus honeybees
• Tetrachromats (four): most birds, many fish and reptiles
• Pentachromats (five or more): possibly pigeons and some butterflies

The common ancestor of all vertebrates was a tetrachromat. Early mammals lost two of the four cone types, probably during a long nocturnal phase when sharp colour vision mattered less than seeing in the dark [3]. That one event explains most of the pattern below: birds, reptiles and fish kept rich colour vision, while most mammals did not.

Dichromatic vision in dogs, cats and most mammals

Dichromatic vision is colour vision based on two types of cone. Placental mammals are, as a rule, dichromats [2]. Dogs, cats, horses, cattle and most other mammals have the kind of colour vision that a person with red-green colour blindness has: they can tell blues, greens and yellows apart but cannot distinguish oranges and reds [1].

Dogs have been tested directly. A behavioural study of three dogs found two classes of cone pigment, with peaks at about 429 nm (violet-blue) and 555 nm (yellow-green), and concluded that dogs have dichromatic colour vision [6]. So a red ball on green grass is hard for a dog to pick out by colour, while a blue or yellow toy stands out.

How many colours a dichromat can see is often put at about 10,000. That number comes from a simple calculation, about 100 shades per cone type multiplied together, not from testing animals, so treat it as a rough guide [2]. The infographic gives 40,000, which is higher than the usual estimate.

Trichromats, including humans and other primates

Humans, apes and Old World monkeys have three cone types, sensitive to short, medium and long wavelengths. Our ancestors re-evolved the third cone after mammals had lost it [2]. One explanation is that it helped primates spot ripe fruit and young, more nutritious reddish leaves against green foliage; another is that it helps read skin flushing in other members of the group [4].

Primates are not all the same. In most New World monkeys, males are dichromats and some females are trichromats, while both sexes of howler monkeys are trichromats [1][4]. Some Australian marsupials, such as the honey possum and fat-tailed dunnart, also appear to have three cone types [4].

Honeybees are trichromats too, but their three receptor types cover ultraviolet, blue and green rather than our blue, green and red [4]. Bees’ vision stops at about 590 nm, so they are largely blind to red, but they can see ultraviolet patterns on flowers that guide them to nectar [1]. Strictly, insects have photoreceptor cells in compound eyes rather than vertebrate cone cells, but the principle of comparing receptor types is the same.

A common estimate is that a human trichromat can distinguish about a million colours (100 x 100 x 100), and some researchers put it above 2.3 million [2]. The 10 million in the infographic is a popular figure but higher than these estimates.

Tetrachromats and pentachromats, birds, fish and reptiles

Tetrachromacy, colour vision with four cone types, has been shown in several species of birds, fish and reptiles [3]. Many birds have a fourth cone sensitive to ultraviolet, and some species have plumage markings that are only visible in ultraviolet light [1]. Teleost fish, the large group that includes goldfish, are typically tetrachromats, and goldfish can see into the ultraviolet (but not the infrared, despite a popular myth) [1][3]. Reptiles and amphibians usually have four cone types, occasionally five, and some nocturnal geckos and frogs can see colour in dim light [1].

Pentachromacy is less certain than the infographic suggests. Pigeons have five or more kinds of colour receptor in their retinas and are believed to be pentachromats, but there is no psychophysical evidence yet that they actually use five colour channels [3]. Papilio swallowtail butterflies have six types of photoreceptor and may be pentachromatic [1].

The figures of 100 million colours for four cone types and 10 billion for five, both from the infographic, follow the same multiply-by-100 logic as the human estimate. Nobody has measured them, so they are best read as an idea of scale rather than real counts.

Monochromats, whales, seals and owl monkeys

Monochromats have one cone type and see in shades of grey from black to white [5]. Two groups of marine mammals are cone monochromats: cetaceans (whales and dolphins) and pinnipeds (seals, sea lions and walruses) [5]. Owl monkeys, which are nocturnal, are monochromats too, unlike most primates, and so are raccoons, kinkajous and a few rodents [5].

The link is light. Animals that live in the sea, come out at night or live underground get little useful colour information, so there is less pressure to keep a second cone and they often lose it [5]. The infographic’s figure of 200 colours for this group doesn’t really hold, since with one cone type an animal cannot separate hue from brightness at all.

Which animal sees the most colours?

Mantis shrimp have the most complex colour receptors known, with 12 to 16 receptor types depending on species, covering deep ultraviolet to far red (300 to 720 nm) [1][7]. You might expect that to mean they see far more colours than anything else, but tests suggest the opposite. When researchers at the University of Queensland tested how well mantis shrimp could tell wavelengths apart, they were surprisingly poor at it. The researchers think mantis shrimp use their receptors to recognise colours quickly rather than to discriminate fine differences [7].

So more receptor types do not automatically mean more colours. In terms of colours actually distinguished, birds and other tetrachromats are the strongest candidates for seeing more than we do, especially as their range extends into the ultraviolet.

Questions about animal colour vision

Do animals see colour?

Most animals see some colour. Most mammals have two-colour (dichromatic) vision, many birds, many fish and reptiles see more colours than humans, and only some groups, such as whales, dolphins, seals and owl monkeys, see only shades of grey [1][5].

What is dichromatic vision?

Dichromatic vision means seeing colour with two types of cone cell. It is normal for most mammals, including dogs and cats, and in humans it is a form of colour blindness. Dichromats can tell blues from yellows but struggle to tell reds from oranges and greens [1][2].

What colours can dogs see?

Dogs see mainly blues and yellows. Their two cone pigments peak at about 429 nm and 555 nm [6], so like most mammals they cannot tell reds and oranges apart, much like red-green colour blindness in people [1].

What animal can see the most colours?

Mantis shrimp have the most colour receptor types (12 to 16), but tests show they are poor at telling similar shades apart [7]. Many birds, with four cone types including one for ultraviolet, probably see more colours than humans do [1][3].

Can any animals see ultraviolet light?

Yes. Bees and many other insects, most birds and some fish, including goldfish, can see ultraviolet light [1].

Sources

1. Wikipedia, Color vision (section on colour vision in nonhumans).
2. Wikipedia, Dichromacy.
3. Wikipedia, Tetrachromacy (includes pentachromacy).
4. Wikipedia, Trichromacy.
5. Wikipedia, Monochromacy.
6. Neitz J, Geist T, Jacobs GH. Color vision in the dog. Visual Neuroscience, 1989.
7. Thoen HH, How MJ, Chiou TH, Marshall J. A different form of color vision in mantis shrimp. Science, 2014.

Last reviewed 5 November 2026