A single variation in a person’s eyes can have them seeing an extra 99 million colors – here’s how it happens.

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We may take for granted the fact that we wake each morning and see the world in color. For a select few, though, it’d be hard to do so. With just one change in the makeup of their eyes, their vision becomes much richer. Stunningly, they can see more colors ‒ 99 million extra shades, to be precise ‒ then everyone else on earth.

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People with this incredible boost in vision see more hues than we could ever imagine. During one test of this ability, three of these extra colors appeared inside in a special light device. Normal eyes can’t perceive any differentiation between that trio of shades. But those with this particular change in their cells? They could see each hue as it flashed before their eyes.

Of course, these people see colors with incredible clarity outside of the lab, too. Perhaps it’s the way light hits the water to create a pinkish glow. Sometimes, they look at pebbles that might appear gray to the rest of us, but they see flecks of yellow, green, orange and blue. Undoubtedly, such vision makes life all the more beautiful.

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And, now, scientists know precisely why some people can see colors with such incredible clarity. The idea came about in 1948, but it didn’t get much fanfare. In more recent years, though, experts have honed in on that initial research. They’ve even confirmed why certain people can see almost 100 million more colors than everyone else. And the cause is a minute one, to say the least.

It’s strange to think that the objects we see don’t have any inherent color. Instead, they absorb certain shades of light and reflect others. What bounces back is what we see – the light hits the retina, which sits to the rear of the eye. And that’s how we determine what hue things are.

For instance, we perceive bananas – ripe ones, anyway – to be yellow. They absorb all light excepts that with wavelengths between 570 and 580 nanometers. So, these then bounce back, and, of course, are the wavelengths that create yellow light. As another example, an apple might absorb all wavelengths except the one we see as red.

Interestingly, we process the color white when something reflects back all of light’s wavelengths. Black, on the other hand, has absorbed all of the different hues. Otherwise, we see everything else as reflections of varying amounts of blue, red and green light. Believe it or not, those three shades create every single visible color on the spectrum.

The retina is responsible for processing all of these wavelength combinations. As such, it’s deemed to be an extension of your brain. Millions of rod and cone-shaped cells cover the retina, and these receptors transform light into nerve impulses. The optic nerve then shuttles these impulses into your brain’s cortex.

Rod and cone cell placements explain facets of our vision beyond color, though. For instance, the former are typically responsible for telling the brain that we see black and white. As such, they tend to be more light-sensitive than their curved counterparts. And the rods appear most commonly around the retina’s edges, making them more responsible for our peripheral vision.

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Therefore, our peripheral vision – mostly determined by the rod-shaped cells – tends to be less colorful than things we see in front of us. But the rods help us in other ways. For instance, when you walk into a dimly lit room, it’s these cells that help your vision adjust to the darkness.

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Meanwhile, the cone-shaped cells reside in the retina’s central region, where they process higher intensity light that hits the eye. These beams create both the color and sharpness of what we see. And cones with different sensitivities – to short, medium or long light wavelengths – help the brain figure out which colors we see.

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Typically, the cones present in the retina mostly process long wavelengths, which produce yellows, oranges and reds. As such, we tend to see more differences between warmer tones than cooler shades. Of course, not everyone is able to see different hues in the same way. About eight percent of the male population, along with one percent of females, in fact, deal with color impairment.

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People with this impairment – also known as colorblindness – cannot tell the difference between particular shades. Most common cases involve a person seeing green and red as identical. This doesn’t mean they can’t see colors at all, but rather that their retina cells transmit information to the brain in a different way.

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Humans, though, aren’t the only ones who can process the entire spectrum of colors. Other mammals, as well as fish and birds, can also see the rainbow of hues. Then, there are those creatures whose light processing goes beyond that of humankind. Take bees as one example, since they can see ultraviolet light.

Still, there are a handful of humans who have color-seeing abilities beyond the norm. One of them is New Yorker Maureen Seaberg, who worked as both an author and journalist in her hometown. She realized that she saw the world differently when she’d go clothes shopping – outfits meant to be matching separates would clash in her eyes.

Seaberg explained to the BBC’s Future website in 2014, “I have always had polite disagreements with people about shades of colors.” And those on the other end of the discussion often had trouble seeing what the author was talking about. This became especially apparent when she decided to redecorate a house – and choose its paint colors.

Ultimately, Seaberg said “No,” to 32 different paint shades before she found the right color. She recalled, “The beiges were too yellow and not blue enough, not cool enough; some of the almonds were too orangey.” Her contractor couldn’t see the hues as vividly as the author did, making the process all the more difficult.

Concetta Antico’s story follows quite a similar trajectory to Seaberg’s. In fact, Antico claimed that she knew as a child that she saw the world in a different light to everyone else. At one point, her mother told her, “You are going to be an artist and art instructor,” she later recalled.

Down the line, Antico fulfilled her mother’s premonition, and her ability to discern colors so minutely gave way to brightly hued paintings that became her signature. She described her process for painting a rainbow eucalyptus, saying, “The tubes of paint were flying. The yellows, the violets, the lime greens… I was ferociously mixing on the palette trying to produce all the streams of color in the bark.”

Antico has shared these incredible color-centric talents with her art students, but they simply could not see what she saw. She recalled, “I’d say, ‘Look at the light on the water – can you see the pink shimmering across that rock? Can you see the red on the edge of that leaf there?’” The students would agree, but, in reality, they couldn’t see the detailed hues that their instructor pointed out.

In the end, it would be one of Antico’s customers who shed light on the artist’s unique vision. They pointed out that she might have the particular genetic condition that causes her to see so many more colors that the average person. The shopper suggested that she reach out to researchers helming a study into the genes responsible for such an effect.

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Indeed, research into this area began in 1948. In that year, H.L. de Vries, a Dutch scientist, uncovered an interesting truth about men with colorblindness. Their retinas had three varieties of cone cells. Of these, two proved normal, while a single mutated cone reduced their sensitivity to green or red light.

On top of that, de Vries discovered another interesting genetic facet. It seems that mothers of colorblind men – or daughters of those males with the mutated cones – had an interesting retinal setup themselves. Namely, the women’s eyes contained four types of cone-shaped cells. They had three functional cones alongside a mutated cone.

Because the women had three working varieties of cone-shaped cells, they could see normally. But no one had ever noticed that those with colorblindness could pass on a fourth type of cone cell. And it wasn’t until the 1980s that scientists looked into the possibility of this fourth retinal cell being a functional part of the eye.

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At that time, Cambridge University’s John Mollon took up the cause. He worked under the assumption that men with colorblindness passed the mutated cones to their female children. And this meant that about 12 percent of women should have the fourth cell within their retinas.

However, Mollon’s research didn’t uncover any women with a functioning fourth cone cell. As such, all of his test subjects perceived color in the same way as the average person. It would take another two decades before Gabriele Jordan, a neuroscientist and ex-colleague of Mollon, could reveal the effect that extra cone could have.

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Jordan’s experiment tested 25 women with that fourth cone cell type. They sat in a darkened room as a light-up device flashed a trio of colored circles in front of their eyes. Those without a functional fourth cell would think that all three were the same shade. But, if that extra cone actually worked, then some might be able to spot the different colors

Only one of the 25 women tested could actually see the differences between the colored rings. And she did so in every single test Jordan administered. As she told Discover magazine in 2012, the neuroscientist could barely contain her glee in proving the theory. She recalled, “I was jumping up and down.”

And with that, Jordan confirmed the theory of tetrachromacy. The rare condition encompasses those including Seaberg and Antico, as well as the neuroscientist’s original test subject. Each woman has four different types of cone cells in her eye which provides a quartet of channels through which to convey color information.

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With that extra cone cell, tetrachromats can see more colors than anyone else. A whopping 99 million additional shades, to be precise. In comparison, the typical trio of cone cells allows us to see approximately one million colors. Those who suffer from color blindness – and have only two functioning cone cells – perceive only 10,000 tones.

Antico and Seaberg knew for a long time that they had honed senses of sight. But, some experts say, other tetrachromats might not even realize their heightened visual abilities. According to Jordan, most wouldn’t even know they could see colors differently as they’d probably never used that special fourth cone.

Vision researcher Jay Neitz, who worked at the University of Washington, backed up that theory. He believes that tetrachromats might have a hard time uncovering their abilities without colors mixed just for them to see. As he told Futurism, “Most of the things that we see as colored are manufactured by people who are trying to make colors that work for [those with three cone cells].”

In Antico’s case, though, she had no problem seeing additional hues without having them mixed for her specifically. University of California, Irvine, researcher Kimberly Jameson worked closely with the artist to better understand her tetrachromacy. She realized that the painter’s extraordinary vision could be seen in her ultra-colorful work.

Jameson told the BBC’s Future, “If you look at [Antico’s] pictures of [the] dawn, she paints a lot of colors and renders them in very low lighting.” In any other case, an artist might simply take creative liberties with the sunrise’s color palette. But the researcher confirmed that Antico simply sees more hues and lighting than most.

Nevertheless, not all tetrachromats have the honed sensibilities that Antico has gained through her career in art and creation. Jameson, in fact, described the artist as “the perfect storm for tetrachromacy, because she has a huge amount of perceptual learning experience by working with color on a daily basis.”

Still, Antico admitted that living with tetrachromacy hasn’t always been easy. Just walking through the grocery store, she said, “is a nightmare.” As the artist explained to the BBC, “It’s like a trash pile of color coming in at every angle.” This type of sensory overload could, however, easily explain her favorite color.

Antico said, “People find it extraordinary that white is my favorite color, but it makes sense because it is so peaceful and restful for my eyes. There is still a lot of color in it, but it’s not hurting me.” Still, despite the downsides of tetrachromacy, the artist hoped to use her ability to help others open their minds.

For one thing, Antico dreamed of developing some sort of training system for tetrachromatic children. A way in which they could learn to reach their full color-seeing potential. Beyond that, though, the artist hoped that her story and skills would help everyone to see the world differently, whether or not they had that fourth cone cell.

And, according to Antico, the latter plan had already started to come to fruition. She said that some of her art students had begun to point out additional colors, thanks to their teacher’s unique cone cells. The art instructor described their discovery of extra hues, saying, “It’s as if a curtain is being lifted.”

The chance to show others more colors had special meaning to Antico. Her daughter came into the world with color blindness because of the gene variation that allowed the artist to see more hues. So, she hoped to use her tetrachromacy to help others see the beauty in everything. She said, ““What if we tetrachromats can show the way to colour for people who are less fortunate than us? I want everyone to realize how beautiful the world is.”