What colours can dogs see?

It was long speculated that dogs were completely colour blind, seeing the world in black and white. In recent years, studies have confirmed that dogs, although not able to see the full colour spectrum as humans, can see limited colour because they have a red-green colour deficiency known as Protanopia. 1% of human males also have this phenomenon. With Protanopia, the eye lacks the long-wavelength sensitive retinal cones making it impossible to differentiate between the green-yellow-red section of the colour spectrum.

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