Are cuttlefish color blind?

By the evidence so far, yes. The common cuttlefish has one visual pigment (492 nm), and in a behavioral test it did not react to color differences once brightness was matched (Mäthger and colleagues, 2006).

How do cuttlefish camouflage if they are color blind?

That is still an open question, according to the same study. The cuttlefish in it noticed differences in contrast of about 15%.

Is the simulator exact?

No. It shows brightness through the one pigment. The pigment curve comes from a template, the eye's lens and the water are left out, each color's spectrum is guessed from its screen color, and the picture is not blurred, because we found no measurement of how sharply cuttlefish see.

How cuttlefish see

The common cuttlefish has a single visual pigment, and a behavioral test found it color-blind. It sees brightness: in our model red comes out very dark, and some blues and yellows become the same gray. How it still blends into colorful surroundings is an open question. Point your camera, or open a photo or video, to see the colors approximately as a cuttlefish does. Drag the line to compare.

Compare with originalComparison line position

Gray, computed from the cuttlefish's only visual pigment (492 nm), so red comes out very dark. Not blurred: we found no measurement of how sharply the cuttlefish sees. A phone camera and screen add their own color shifts.

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One pigment, tested color-blind

Mäthger and colleagues (2006) used a reflex of the common cuttlefish, Sepia officinalis: on a black-and-white checkerboard it shows a high-contrast body pattern. They paired one green with grays from white to black, and a blue with a yellow, with the colors matched in brightness for the cuttlefish's only visual pigment, which peaks at 492 nm. Where the two colors of a board were equally bright for that pigment, the animals did not show the checkerboard pattern, as if the ground were uniform, and the authors conclude that cuttlefish must be color-blind. The animals did notice objects that differed from the background in contrast by about 15%.

How a color-blind animal manages its camouflage in colorful surroundings still remains a question, the authors note.

What one pigment means for colors

With one pigment, two colors look different only if one is brighter for it. The simulator turns each color into a gray as bright as the 492 nm pigment finds it. Red comes out very dark, because that pigment responds very little to red light, and in the table below the blue toy and the yellow toy come out almost the same gray.

The table gives the color difference (ΔE 2000) for a person and for the cuttlefish model: the smaller the number, the harder the pair is to tell apart. On the scale we use across this site, below 3 is a close match, 6 or more is a visibly different color, and 10 or more is clearly different.

Orange toy and green grass

YouΔE 46Common cuttlefishΔE 3

Red ball and dark green pine

YouΔE 55Common cuttlefishΔE 3

Blue toy and yellow toy

YouΔE 73Common cuttlefishΔE 1

Yellow toy and gray

YouΔE 30Common cuttlefishΔE 3

How the simulator works

For each color the simulator estimates how strongly the 492 nm pigment would respond, using the pigment template of Govardovskii and colleagues (2000) and daylight (CIE D65), and shows a gray of the same brightness; white and grays stay as they are. The signal weighs the light by its energy; weighting by photon count instead would change some grays by up to 8 of 255 in our check. It is an approximation: the eye's lens is left out, the light is daylight in air, not under water, and each color's spectrum is a guess from its screen color. The picture is not blurred: we found no measurement of how sharply cuttlefish see. Everything runs on your device: the camera picture, photos and videos are not uploaded.