Question: Are dogs colour blind?

Hi cnixon,

Dogs can’t see colour as well as people, but they aren’t completely colour-blind.

People have three kinds of cell in the eye that detect colour; one detects light that’s in the red part of the spectrum (rainbow), one for green, and one for blue. We “see” different colours depending on “how much” light each of the three kinds of cell detect.

Most other animals, including dogs, only have two kinds of colour-detecting cells, and so they can’t distinguish “different colours” as well.

The question raises a more important point about colour: that what the eye sees and what is “really there” (that you could measure with scientific equipment) are two very different things.

For example, if you had a red laser and a green laser that somehow didn’t damage your eyes, and you shone both lasers at the same part of your eye, your eye would say, ‘I see a yellow dot’. If you shone the lasers at a scientific detector, the detector would say, ‘I see red light and green light.’ But you could also have a true yellow laser that both the detector and your eye would agree is yellow.

In physics/chemistry, the ‘colour of light’ means the frequency/wavelength of the light. But the light around us in everyday life is almost never of just ONE frequency/wavelength: it’s a mix of many different frequencies/wavelengths. The eye interprets this mixture and tells your brain what pretty colour to “see”.