Color May Not Actually Exist. Here’s the Unsettling Reason Why.

Here’s what you’ll learn when you read this story:

• There’s an ongoing argument that color isn’t actually real, but rather something we perceive because of the way our eyes process light.
• Human eyes see only a small fragment of the light spectrum, but the photoreceptors in our retinas are activated by the light that objects reflect—and that’s what we experience as color.
• Wavelengths can be measured, but color itself might be a quale: a sensory experience unique to each person, and one that can’t be quantified from the outside.

In Lois Lowry’s 1993 novel The Giver, 11-year-old Jonas lives in a dystopian society that engineered away difference in the name of “Sameness.” Part of that involves genetic engineering that leaves everyone colorblind—which is why Jonas is so bewildered when he’s gazing at Fiona, a girl in his class, and her hair suddenly does something he can only describe as “changing.” He can’t process what he’s just seen, and he wonders what could have put him in such a trancelike state during those few fleeting seconds. Fiona’s hair, it turns out, is red.

In a sense, there’s no such thing as color—at least not as we think we know it. Jonas may be mostly colorblind, but what the rest of us think we see is just the result of sunlight interacting with our surroundings. Photons of different wavelengths strike objects and create an illusion when they’re reflected into our eyes. Plenty of neuroscientists would agree with the premise behind that scene in The Giver: hypothetically, someone seeing color for the first time would be at a loss to describe it, even if they’d already learned everything there is to know about how color works. For that matter, it’s nearly impossible for those of us who do see color to describe what it actually is. A plethora of adjectives can be attributed to red, but color is ultimately subjective—as the 2015 dress photo that turned into a cultural phenomenon proved.

Part of the problem is that humans can only see a fragment of the light spectrum. Our vision is limited to the narrow band of wavelengths between ultraviolet and infrared, though we still manage to make out as many as 10 million colors within it. That’s why the most powerful telescopes are tuned to detect wavelengths our eyes could never process, picking up evidence of black holes, supernovae, and extremely distant stars in everything from gamma rays to radio waves. Data from these telescopes, which would otherwise be invisible to us or appear as little more than blurs of light, is translated into color so we can make sense of it.

Closer to home, the process is more direct. Light that isn’t absorbed by an object is reflected, and it enters the eye through the cornea, the eye’s outermost layer, which bends that light toward the pupil. The pupil—widened or narrowed by the iris around it—controls how much light reaches the lens. The lens then focuses that light onto the retina, where it hits cells that react to it.

Those cells are photoreceptors, and they come in two flavors. Rods are stimulated in dim light but can’t distinguish wavelengths, which is why we see only shades of gray when an environment is too dark. Cones, on the other hand, contain photopigments that respond to brighter light and are sensitive to its various wavelengths, so they’re the ones responsible for color vision. Each type of cone is most sensitive to roughly red, green, or blue wavelengths. Depending on the wavelengths an object reflects, one or more types of cones are activated, and they transmit a signal through the optic nerve to the brain’s visual cortex. Experience fills in the rest: because your brain accounts for the light an object is sitting in, you’ll still perceive a familiar object as its usual color even under tinted lighting.

Perceive is the operative word here, because it might be that color is a quale. Pronounced KWAH-lay, the concept is controversial among scientists and philosophers alike. Qualia are sensory experiences that are unique to every person and can’t be quantified by physics. The wavelength of red is measurable, but the way Jonas sees Fiona’s hair is his and his alone. The same idea can explain why different people tasting the same dish often describe different flavors and sensations—descriptions that still overlap, because they share the same physical reality.

Other factors can nudge color perception, too. That 2015 dress, which was eventually revealed to be blue and black rather than white and gold, was more likely to look blue and black to people who prefer to stay up late and sleep in; early risers, whose brains are more accustomed to daylight, tended to see white and gold. Glare warped its colors either way, so even the netizens who called blue were surprised by how dark the dress looked once the image was adjusted.