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It’s easy to believe that color is something stationary. But in reality, colors and their shades hide a realm of enigma. They appear in perplexing mathematical challenges and in the strange features of animals.
The most intriguing mysteries revolve around the relationship between humans and color. Whether it’s people who can 'hear' colors or perceive emotions in shades, green and all other colors will never appear the same again.
10. Various Hominids Embraced the Color Red
Red was likely the first color widely used by humans. This trend started in prehistoric times, but it may not have been driven by the vividness of the hue itself—its real advantage was the abundance of ocher.
This natural pigment was easily accessible and simple to use. It didn’t fade, though it could stain skin and walls. The earliest users of this clay weren’t even modern humans. The oldest discovery of ocher pieces, 70 in total, came from a site where Homo erectus inhabited 285,000 years ago. Neanderthals also utilized it around 250,000 years ago. Some of the earliest Homo sapien artifacts made with ocher include a shell containing a blend of the pigment, fat, and charcoal, dating back around 100,000 years.
Ocher had many other uses as well. It was applied to color graves, tan animal hides, repel mosquitoes, treat illnesses and skin conditions, and carry symbolic meanings. It was also used in the creation of glue and plant treatments. Ocher’s use continued for centuries, even by artists during the medieval and Renaissance periods.
9. Why Water Stains Appear Darker
Although water itself is colorless, it has the effect of darkening the appearance of materials. There’s a fascinating science behind this phenomenon. The darkening is not due to the fabric’s composition or the fabric actually becoming darker. Rather, it’s an optical illusion caused by the interaction of wavelengths with the human eye.
When light interacts with an object, two things happen. The object both absorbs and reflects certain amounts of light. The reflected wavelengths that bounce off an object and back into the eye are what create the perception of color. For example, a yellow cloth absorbs all wavelengths except those corresponding to yellow. The color we perceive is simply the shade of wavelengths being reflected.
Dry and wet surfaces handle light differently. Wetness, such as from water or sweat stains, alters the angle of light in a way that more yellow wavelengths are reflected into the cloth rather than reaching the observer's eyes. This causes a wet area to appear darker than the surrounding dry fabric, which reflects more color back into the viewer's vision.
8. The Enigmatic Colorful Crab
The coconut crab, native to the Indo-Pacific, is a two-toned mystery. These giant land crabs, known for their love of coconuts, come in three different colors. As juveniles, they are white, which is typical from a scientific standpoint, as the pale color is associated with their youthful stage. However, once they mature, these crabs randomly transform into either a striking blue or red.
Numerous attempts to uncover the reason behind this color change have been unsuccessful. There’s no clear explanation as to why some crabs turn red while others take on a blue hue. Extensive testing on hundreds of crabs revealed that the color variation isn’t related to factors like gender, location, camouflage, mate attraction, specific behavior, or any other physical characteristic. There’s no obvious advantage to being either color, and no noticeable competition. Both blue and red appear in equal measure.
A solid explanation for why coconut crabs exhibit both colors surely exists, but it remains a mystery. DNA research may hold the key. In the future, scientists aim to identify the genes responsible for each color and those associated with the crabs’ vision, which could reveal whether these creatures are capable of perceiving blue and red.
7. The Enigma of Blue
The human eye can distinguish approximately a million different hues, but blue was a late arrival. In the 1800s, scholars examined Homer’s epic poem The Odyssey, and found that it made no mention of the color blue. Instead, Homer used unusual descriptions, like calling the sea “wine-dark.”
In the years that followed, scholars analyzed scripts from Hindu, Chinese, Icelandic, Arabic, and Hebrew cultures. None of them contained a word for “blue.” The first people to reference the color were the ancient Egyptians, who held the secret of blue dye production. Modern scientists are exploring whether this cultural absence of the term “blue” implies that humans could not originally perceive the color.
A fascinating study published in 2006 revealed that the Himba tribe in Namibia has no distinct word for “blue” and does not differentiate it from green. When tested, members of the tribe had difficulty identifying one blue square among eleven green ones.
However, the Himba tribe possesses an incredible ability to recognize different shades of green that other people fail to notice. Such studies indicate that while blue may have been present throughout history, it wasn’t until recently that the human eye began to distinguish it as a separate hue.
6. The Mystery of Toxic Green Blood
The New Guinea skink is truly peculiar. On the outside, it appears to be a typical lizard. But inside, nearly everything takes on a green hue, from its blood to its skeleton, muscles, and membranes.
Normally, blood is red due to hemoglobin, the pigment responsible for oxygen transport. However, the New Guinea skink's blood contains an additional pigment, biliverdin. As red blood cells break down, biliverdin is produced, and in large amounts, it masks the red of hemoglobin. Such high concentrations are toxic. Humans and other species have mechanisms to remove this pigment from their systems.
A groundbreaking study in 2018 provided some insights into these strange creatures. After mapping a family tree of over 50 types of Australasian skinks, scientists found that the green-blooded skinks were not closely related. This discovery revealed that the evolution of toxic blood and tissues occurred independently in five different species.
The repeated appearance of biliverdin dominance in unrelated skinks suggests that it wasn’t a random mutation. Scientists still cannot explain the benefits of green blood or how these reptiles survive what amounts to an overdose of biliverdin.
5. The Troxler Effect
Ignaz Troxler, a Swiss doctor and polymath, may not be a household name, but his legacy persists in the curious phenomenon known as the “Troxler effect.” Fascinated by colors and objects that seemed to fade from view while still within his vision, he documented his observations in 1804. This disappearing act recently gained attention online, particularly through an image filled with soft pastel hues.
When staring at the image (as shown above), the colors seem to vanish almost as if by magic. Once the viewer’s focus shifts, the colors abruptly return. While scientists generally agree with Troxler’s theory that peripheral vision eventually erases static details, modern understanding has refined the explanation of this effect.
The Troxler effect occurs to everyone every day. Without it, most people would feel overwhelmed. Our brains are constantly bombarded with stimuli, and the brain compensates by fading out anything it deems irrelevant. This is why we often forget the clothes we’re wearing or the fact that our noses are visible.
The disappearance of the pastel page’s content occurs because the peripheral details blend into the surrounding white. This happens when retinal cells receive no new information, tricking the brain into dismissing those details, creating the illusion of emptiness.
4. Dinosaur Colors Live On
Numerous modern bird species lay eggs with stunningly colorful shells. In a recent discovery, researchers found that the same two pigments responsible for these vibrant eggs—protoporphyrin and biliverdin—also appeared in the eggs of an oviraptor, a small dinosaur with birdlike features.
To delve deeper, scientists expanded their study. They analyzed eggs from living bird species, such as terns, emus, and chickens, and compared them with fossilized eggs from 15 Cretaceous species and extinct birds. What they uncovered debunked the long-held belief that the colorful shells of bird eggs are a relatively recent phenomenon.
The two pigments were found in much older eggs, particularly those of eumaniraptoran dinosaurs, the very ancestors of modern birds. Astonishingly, some of the eumaniraptoran eggs even featured patterns and pigmentation depths comparable to today’s bird eggs.
The vibrant camouflage likely came about when some dinosaurs transitioned from hiding their nests underground to keeping a watchful eye on their eggs in open areas. This means that colored shells evolved millions of years before the birds that now lay them.
3. People Who Hear Colors
Approximately 4 percent of humans experience a fascinating condition called synesthesia, where sounds can evoke colors. This phenomenon is not imaginary; brain scans show that both the sight and sound regions of the brain light up when a person experiences it.
While much is still unknown, some aspects of this unique condition are understood. For those with synesthesia, a sound or word can immediately trigger a corresponding color in their mental image. The condition is also found in individuals whose brains have a greater number of connections between sensory regions than typical.
In 2018, a study took a genetic approach to explore the mysteries of synesthesia, which often runs in families. Three groups of participants, spanning three generations each, were selected. All participants experienced the sound-color form of synesthesia, where sensory experiences overlap.
DNA sequencing revealed 37 genetic variants that could be responsible for the condition. Upon investigating the biological functions of these genes, one process stood out: axonogenesis. This makes sense, as axonogenesis plays a crucial role in wiring the developing brain, explaining why those with synesthesia tend to have more connections between sensory areas of the brain.
2. Hadwiger-Nelson Breakthrough
The Hadwiger-Nelson problem is an intriguing mathematical puzzle first introduced in 1950, and it remains unsolved. The riddle seems simple: Imagine an infinite plane with colored points connected by lines. How many different colors are needed to ensure that no two points of the same color are connected?
Soon after the Hadwiger-Nelson problem was introduced, mathematicians quickly realized that a limitless plane would only require between four and seven colors. However, they were soon stumped. For decades, no one could figure out the precise number of colors needed.
In 2018, an amateur mathematician shook the math world with his findings. Aubrey de Grey, who enjoys solving mathematical puzzles in his spare time, proved that at least five colors were necessary, debunking the earlier assumption that only four would suffice.
His breakthrough came as he worked with the Moser spindle—a geometric shape with seven points and 11 lines. By assembling a large number of spindles and adding various other shapes, he refined the number of colors needed by linking 1,581 points together.
The fewer the points in the graph, the more successful the result. Thanks to de Grey's work, mathematicians have since been able to connect 826 points using only five colors, without any of them touching.
1. Humans Change Color
In 2018, researchers discovered that idioms like “green with envy” weren’t just figurative language. Depending on one’s emotions, human faces genuinely change color. This subtle chameleon-like ability, related to blood flow, often manifests as such faint hues that others usually notice it on a subconscious level, revealing the person's true feelings.
The color changes are primarily around the eyebrows, cheeks, chin, and nose. Using computer programs and an understanding of how humans perceive color, scientists were able to identify facial 'rainbows' for the first time.
For example, disgust appeared as a blue-yellow hue around the mouth, while the forehead and nose showed red-green tones. Happiness turned the cheeks and temples red, but oddly, the chin showed a hint of blue. 'Surprise' closely resembled happiness, except the forehead had a deeper red tone and the chin was less blue.
When shown images of neutral expressions, volunteers were able to correctly identify the emotion when colors were overlaid on the face. In other images, the wrong colors were applied, such as happy hues on an angry face. Even though they couldn't pinpoint the issue, the volunteers could instinctively sense that something felt off.
