How Many Colors Can We See?

You might tend to assume that everyone sees
the world in pretty much the same way, within the same sets of colors that we call visible
light, as if we were all coloring with the same box of crayons. But the truth is, how many colors you can
perceive actually depends on what you’re working with. Our eyes are these amazing energy converters,
taking light energy and turning it into chemical energy and transmitting it to our brains through
nerves. And within our retinas at the backs of our eyes are receptor cells called cones
and rods. Rods allow us to see in black and white and
grey, and they’re still effective in dim light, and most humans have more than one hundred
and twenty million of them. Cones on the other hand are they eye’s color receptors, we only
have six million of those, and they enable us to see fine detail in well-lit conditions. Most people have three types of cones: blue,
red and green, and each receptor is triggered by different wavelengths of light. The brain
combines the signals from the three types of receptors to produce what we perceive as
color. When you put all the various combinations from these three receptors together, most
humans can see about one million colors. This is called trichromacy. Color-blindness usually occurs when a person
is missing one of those cone receptors – almost always either red or green. This is called
dichromacy, and it reduces the ability to distinguish between those two colors. Interestingly, there are varying degrees of
color blindness. Dichromatics can see about ten thousand colors, but humans with monochromacy,
who are missing two or all three types of cones, only perceive about one hundred colors
– mostly shades of grey. And because the genes that affect color vision
are on the X chromosome, disparities in color vision often correspond with your sex. Biological males only have one X chromosome,
so they’re more likely to inherent color blindness – about 8% of men have some form of it. But
biological females have two X chromosomes, so for them to be affected they have to have
the color blindness trait on both of their sex chromosomes. As a result, color blindness
in women is really rare, showing up less than 1% of the time. But the X chromosome is also where scientists
have recently found a genetic mutation that may be linked to a sort of technicolor superpower. In 2010, British scientists identified the
first known Tetrachromat – a woman whose eyes has a fourth type of cone that can register
shades between red and green – basically enabling her to perceive at least one hundred million
colors. This, too, seems to be a sex-linked trait,
and other studies have suggested that as many 3% of the world’s women may have this ability,
in which case paint companies and crayon makers are gonna have a lot of new names to come
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