Last year, Jason Allmon received a Father’s Day gift that went well beyond the hackneyed tie or mug; he got something that changed the way he saw the world. His family gave him a pair of glasses designed to help colorblind people, like Allmon, perceive colors better. Upon putting on the glasses and going outside, he gasped and pulled his hand to his mouth. “Shit, what’ve I been missing?” he wondered. Wiping a tear from his cheek, he turned to his wife. “Hey, beautiful. You’re not even the same color I thought you were.”

These glasses, made by a company called EnChroma, have become the center of an online phenomenon: Colorblind people put on the glasses, record their reactions, and post the videos on YouTube, as Allmon did. Many people receive the glasses as presents, with the gift giver filming the moment. The recipients look at the sunset, or their children’s eyes, and report how different, how amazing, how colorful they look. Heartfelt hugs are shared, tears of joy are shed. It’s touching, heartwarming stuff; a friend of mine sometimes treats herself to a few of the clips when she’s feeling down.

I watched these videos with special interest: I, too, am colorblind. So, after seeing other people get bowled over by the glasses, I decided to try them out. I put them on, took long walks outside with my head on a swivel, snaked my way through supermarket aisles lined with gaudy packages, and sought out any flowers I could find. There was no doubt that colors looked more lively and saturated, some dramatically so. I felt I could probably pick out some colors more accurately, discriminate some hues that sometimes confuse me. But while everything looked quite nice, I didn’t see amazing new rainbows. No tears of joy; the Earth did not move.

The glasses clearly worked for me in some sense—but why was my experience so different from those in the dramatic videos? Answering this question led me on a walk through what we know about color vision, to the limits of what science can tell us.

* * *

“Colorblindness” is almost always a misnomer. In the vast majority of cases, people can still see many colors, but they can’t discriminate as many as people with regular vision. The disorder—which scientists prefer to call “color-vision deficiency,” or CVD—comes from problems in the retina, in any of the three kinds of cone cells that detect different colors. Usually the cones most sensitive to red or those most sensitive to green are defective. This decreases the distinction between red and green hues, bending them all toward a muddled brown. It also interferes with perceiving other colors that include red or green, like purple and pink.

Colorblindness doesn’t seem to present much of a practical obstacle to most people who have it. I first ran into this deficiency as a boy, when I had a toy gun and would often lose its red, plastic bullets if I shot them into the lawn. When I took a colorblindness test in the school nurse’s office, I soundly failed it. Over the next decade, I wore many loudly disjointed outfits, until I learned that I couldn’t trust myself with certain colors and combinations.

But while colorblindness seemed to be largely a harmless quirk for me, EnChroma and some researchers say CVD can be a real problem for kids, since information is often color-coded in classrooms. Students can apparently get categorized as learning disabled simply if they’re colorblind. And severe forms of CVD can keep people out of certain jobs, like being a pilot. Beyond the practical issues, many colorblind people have a nagging thought that they’re missing some of the visual enjoyment the world has to offer. We grudgingly accept that most people see more colors, more vivid colors, never knowing exactly what that looks like.

Don McPherson, the chief scientist and cofounder of EnChroma, says their glasses can help those with red-green colorblindness see more of these bright, beautiful colors that other people see. The idea was born when McPherson was working on the optics in glasses made for doctors performing laser surgery. In addition to protecting the surgeons’ eyes from potentially blinding laser light, the glasses make features like blood vessels stand out with greater contrast. When McPherson brought a pair to an Ultimate Frisbee game, a colorblind friend put them on and, looking at orange cones standing on the grass, said, “Dude, for the first time, I can see the cones.”

McPherson’s interest was piqued, and he spent several years tinkering to improve the effect. The goal was to coat lenses with special materials that act as “notch filters,” precisely blocking some of the wavelengths of light that overlap too heavily in the cones of people with red-green colorblindness and cause confusion. This increases the difference between red and green, making many colors look more saturated and easier to distinguish.

One challenge to this effort is that there are many different genetic mutations that cause red-green colorblindness, which comes in various versions and degrees. EnChroma makes two different types of its glasses, but those rough categories can’t cover the disorder’s whole range. The company’s online test found that I have a mild defect in my green cones, which jibes with my perception of my perception. (Scientists pooh-pooh these at-home tests because they’re subject to lots of variation in monitors and lighting conditions, but they may be good enough to get a rough read on your vision.) Since my CVD is apparently not severe, my color vision simply may not have that much room to improve. Mild CVD, mild improvement, mild wow factor.

But colors are a lot more than what happens in cones. They’re not facts reported from our retinas; they’re thoughts, created in our brains, incorporating the signals moving upstream from our eyes with other information from memory, expectation, and context. Exactly how this disparate data is combined to make a single cohesive experience of color is a great ongoing mystery. It may also help explain why people have different reactions to EnChroma’s glasses.

* * *

One of the most important aspects of human vision is color constancy. If you look at an orange in the cool, white light of midday, in the golden light of the setting sun, or in the very warm tones of a fireside, your eyes will receive very different combinations of wavelengths—yet it will look essentially the same reliable orange in every setting.

Scientists have been trying to explain how this happens for more than a century. Some of the leading explanations say color constancy works like the way that cameras automatically find a photo’s “white balance”: By looking at a scene, we deduce the color of the overall lighting and then discount that bias to figure out the underlying colors of what we’re looking at. Other research suggests that memory also plays a role. For instance, banana-shaped outlines have been shown to be perceived as slightly yellow, even if they’re completely neutral-colored. Rosa Lafer-Sousa, a Ph.D. student researching color vision at MIT, says color constancy likely depends on several different processes happening in different parts of the brain, which then combine to produce an overall judgment of color.

However it comes about, color constancy is generally accurate and consistent between people—generally. But consider “the dress,” the subject of a photo that monopolized the internet for several days in late February of 2015. Some swore the dress was clearly blue with black lace; others insisted, just as adamantly, that it was white with gold lace. As in the Civil War, even families were divided. Kanye West saw blue and black, Kim Kardashian saw white and gold (and wondered which of them was colorblind).

Many commenters were shaken by the fact that the people around them could see colors so differently. One of the very first people to see the photo posted it on Facebook, writing, “Is this dress white or gold, or blue and black? Me and my friends can’t agree and we are freaking the fuck out. … I CAN’T HANDLE THIS.”

Color scientists had never seen an image that provoked such divergent responses, and they’ve been unable to create another one since. They say the photo’s inscrutability had to do with its poor quality and unclear lighting conditions. If you assumed the dress was in a warm, artificial light, you would discount some of the reddish light and conclude it was blue and black; if you assumed it was in daylight, you would discount some of the blue tones and conclude it was white and gold. People latched on to incomplete scraps, and based on how they processed the scene, they could settle on either of two very different explanations.

Wearing EnChroma’s glasses may be another of the rare ambiguous situations that reveal people’s visual idiosyncrasies. There have been no systematic studies of how wearing EnChromas affects colorblind people, but the company has some revealing anecdotal data. For one thing, they’ve noticed that some people must wear the glasses for a while before they see the full effects; the company recommends keeping them on for at least 15 minutes solid. (That’s more challenging than it sounds. There’s a powerful temptation to repeatedly take off the glasses for quick comparison.) The time isn’t just for the wearers’ eyes to adjust; it’s for their brains to take in the novel information and incorporate it into their visual algorithms. EnChroma has also gotten reports that some effects persist even after people take the glasses off, but again, the effect varies between individuals.

Looking at the world through colorblind eyes is, in a way, like looking at the dress: There’s an inherent vagueness about how color information should be interpreted. People with CVD are used to the way things look in their everyday lives, but when they put on the glasses, that muddy area between green and red suddenly appears different, presenting signals the wearers have never experienced before. How their visual machinery processes that new information ultimately may be personal.

* * *

Considering how color fits into our visual world, it makes sense that some people are so emotionally affected by EnChroma’s glasses. Seeing luminance, or levels of brightness, is usually enough to determine the shapes and locations of objects, the basic factual information we get from vision. You can recognize Elizabeth Taylor in black-and-white pictures without her distinctive violet eyes, just by differences in luminance.

Color, on the other hand, tends to carry especially meaningful, emotional information, says Lafer-Sousa. Scientists have long hypothesized that mammals’ color vision evolved to judge the ripeness of fruits—not to identify them, which is easy enough in black and white, but to decide whether they’re good or bad. The theoretical neurobiologist Mark Changizi argues that color vision in humans—specifically, the heavily overlapping red and green cones that EnChroma’s trying to set straight—is optimized not for picking fruit but for reading the colors that reflect emotions in other people’s faces: the paleness of fear, the flush of anger, arousal, or embarrassment. (Changizi finds that most of the primates that have three-color vision, like us, also have mostly hairless faces—and mostly hairless butts, which can send clear sexual signals, if your species doesn’t wear pants.) Many people have favorite colors; few have favorite shapes.

Predicting how colors are connected to emotions gets into perplexing questions of psychology. Humans have a huge range of psychological make-ups, and each of us has a unique lifelong story of color associations. What’s more, people’s feelings are heavily influenced by context. The stars of EnChroma videos are in an unusual situation: They are on the spot, performing for a camera, often in front of loved ones who’ve given them an expensive gift. I tried on the glasses by myself, with the critical eye of a reviewer, using a pair loaned to me by EnChroma. It’s very possible that the expectations of those moments affected our differing subjective experiences.

Ultimately, I found clues about why people experience the glasses in different ways, but not a concrete final answer. It’s perhaps not surprising, considering that we still can’t solve a mystery of color that people have been discussing far into the night at least as long as there have been dorm rooms: whether your red is the same as my red.

I think the most revealing thing about this puzzle isn’t the answer but the question. It’s always posed almost precisely the same way: We don’t ask whether your round looks like my round, or your rough feels like my rough, or your sweet tastes like my sweet, or your smell of roses is like my smell of roses. Perhaps this is because color is a personal and meaningful part of each person’s perception of the world, like taste and smell, yet also easily measurable and reproducible, like sound and shape. Rooted at the intersection between our internal and external experiences, color invites us to share our private thoughts, and perplexes us when others do not agree.