This is a very common question asked of veterinarians and pet lovers alike! Color vision is a complicated system that is affected not only by the wavelength of light (color), but also what cells make up the retina of the animals and how many of those cells perceive light and dark. The world of color vision is animals is fascinating.
To help answer this questions let’s start by simplifying the basics of color vision. Humans can basically see 3 wavelengths of light, special structures known as opsins in their retina absorb the specific wavelength. So for the purposes of this discussion we humans have a red opsin, a green opsin, and a blue opsin.
Next it is important to clarify a common misconception in order to better understand dog vision. Most so-called color blind people are not truly color blind. They are only missing the ability to see one of the three wavelengths of light. They are dichromats – they see 2 wavelengths of light, either missing the green or red. It is in fact extremely rare for someone to be truly color blind (0.00003% of people!).
To contrary to popular misconception, dogs do not see in black in white. Their color vision is comparable to color-blind people. They see two wavelengths of light. In simple terms dogs have blue and red opsins, but lack the opsin that absorbs the green wavelength of light.
So what about other animals?
Horses have green and blue opsins, so they detect blue and green! Now this doesn’t mean that they cannot see in red, it just means that a red apple appears in a different shade. These nuances of color vision, such as seeing different shades of a specific color, such as pink can be due to the light of the environment. Something may appear dark red at night, but bright red in the sunlight! Also there can be absorbance of different wavelength simultaneously, for example seeing the color purple is the combination of red and blue together.
Are any animals truly color blind? Yes! This is usually seen in deep-sea fish, they can only see shades of grey. Interestingly marine mammal species only see in red, which means that for seals, whales, and dolphins, the ocean is not blue!