Source: AZ Animals (Extract)
Posted: May 20, 2023

If there’s a cat in your life, you’ve probably caught yourself staring into those big, beautiful feline eyes. A cat’s eyes are among its most glorious features. Read on to find out the science behind cat eye pigmentation, and the rarest cat eye colors that the feline eye can display.

The color of a cat’s eyes is dependent on a pigment called melanin. It’s a substance that determines hair and skin color, as well as eye color, in animals (humans included). Melanin in the iris, the ring of muscle that opens and closes the pupil of the eye, is a big determiner of a cat’s eye color. More melanin will result in darker-colored eyes. But melanin isn’t the only factor. The scattering of light within the iris affects the eye’s apparent color, and that’s influenced by the particular structure of each cat’s eyes.

The result of the above factors interacting is a hugely diverse range of possible eye colors for cats, with nearly endless variation between one shade and the next. But broadly speaking, we can say that cat eye colors occur in a range from blue, with the least amount of melanin, through green, to yellow, and different shades of orange, with dark orange or brown eyes having the highest melanin content. And beyond that, there are rare conditions that add a few unusual variations to the menu. Since all of these factors are influenced by genetics, some cat breeds are known for particular eye color traits. Some eye colors are genetically linked with a particular fur type. For example, cats with a “pointed” fur color pattern—that is, dark color on the face and paws with a light-colored body—will have blue eyes. But for the most part, fur color and eye color are unrelated.

Let’s go eye-to-eye with cat eyes, and see which hue is truly the rarest. Keep in mind that these colors occur on a continuum, with no clear boundaries between them (except for blue eyes, which cats either have or don’t).

Blue Eyes, All Cat Have Them

Or at least they do at the beginning of their lives. That’s because kittens are born without any melanin in their irises. That beautiful hue is the result of the way light is bent as it travels through the eyes, similar to the way light refracting through water vapor in the air creates a blue sky. In most kittens, melanin production kicks in, and by week six or seven the cat’s mature eye color will be evident. But in some cats, the iris never produces significant amounts of melanin, so they retain their baby blue hue. Blue eye color in adult cats is probably the second-rarest color for cat eyes.

Green Eyes Have a Little Bit of Pigment

The combo of some melanin in the iris, plus the light refraction mentioned above, results in green eyes for a cat. While fairly common, it’s a somewhat rarer color than others. We might put green cat eyes in the middle of the common-to-rare spectrum.

Yellow is the Most Common Color for Cat Eyes

As the melanin content of the feline iris increases, cat eye color moves from green into shades of yellow or gold. This is generally considered to be the most common eye color for our feline friends. Of course we’re not saying that your yellow-eyed cat is common; we know you have the most special amazing furball to ever walk the earth.

Orange/Copper/Amber/etc. is the Rarest Eye Color for Cats

As melanin production maxes out, cat eyes take on a deep orange color, which can look copper or even brown. These darkest of cat eyes are also the rarest type, with blue (in adults) taking the second-rarest slot. Except there’s one more scenario to consider…

A Genetic Phenomenon Can Create Crazy-Colored Cat Eyes

Some cats inherit genes that cause heterochromia, meaning their eyes are two different colors. Sometimes this condition is called “odd eyes.” Heterochromia can happen in humans, too, but it’s rare. In cats, it’s not uncommon, though it’s less common than the colors listed above. A cat with differently-colored eyes will always have one blue eye, because the genetic quirk blocks melanin production in one eye. And as mentioned, an eye with no pigment appears to be blue. Heterochromia can occur in any type of cat. But because the heterochromia gene is linked to the gene for white fur color, the condition is most common in cats with white coats.

Sometimes a cat’s genetics only partially affect the melatonin production in one eye. The result is called dichromia, meaning that the affected eye contains two different colors. Sometimes one section of the iris is a different color than the rest. In other cases, the iris may seem haloed or spiked with a second color. Dichromia is the rarest cat eye coloration of all.

So depending on how you look at it, there are three rare eye colors for cats. Dark orange is the rarest of the standard model cat eye. But “odd eyes,” if we consider that phenomenon to be a color, is a rarer occurrence. And if your feline companion has a dichromatic eye, know that you’re viewing something truly exceptional every time your cat stares back at you.