Red

• 1. Introduction

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  Red sits at the long-wavelength end of the visible spectrum, stretching from roughly 625 to 750 nanometers, and no other color has worked its way so deeply into human life. Inside cave 13B at Pinnacle Point on the coast of South Africa, paleoanthropologists found in 2000 that people were grinding ochre as far back as 170,000 years ago. That grinding was almost certainly for body decoration. The questions that follow from this single fact are enormous: why does one color inspire reverence and terror at the same time? Why does it mean love in one culture and warning in another? And how did a pigment scraped from iron-rich clay become the color of revolutions, religions, and road signs across the entire planet?

• 2. How the Eye Makes Red

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  Human eyes register red when incoming light falls between approximately 625 and 740 nanometers. That perception depends on the L-cone cells of the retina, the long-wavelength receptors, responding while the short and medium-wavelength cone cells stay largely unstimulated. The light just past the red boundary is called infrared, meaning below red, and it cannot be seen at all, though the body can sense it as heat. Many mammals, including dogs and cattle, are dichromats: they detect blues and yellows but cannot tell red from green. Both appear to them as varieties of gray. Bulls, for instance, are not reacting to the matador's red cape during a bullfight; they are agitated by its movement. One theory for why primates eventually evolved the ability to see the full human range of colors is that detecting red allowed ripe fruit to be separated from unripe fruit and from inedible leaves. Red light is also used to preserve night vision in low-light conditions, because the rod cells responsible for seeing in dim environments are not sensitive to it.

• 3. Pigments Across the Centuries

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  Red ochre, a clay colored by iron oxide, was among the very first pigments put to human use. The cave of Altamira in Spain holds a painting of a bison made with red ochre that dates to between 15,000 and 16,500 BC. A different source of red came from the Kermes scale insect, whose dried female bodies were crushed to produce dye beginning in the Neolithic Period. Jars of kermes were found in a Neolithic cave-burial at Adaoutse in Bouches-du-Rhone, and the Romans later imported kermes from Spain to color their togas. For brilliant red costumes in the Renaissance, dyers turned to cochineal, an insect from Latin America also used by the Aztecs and the Paracas culture. From the 16th through the 19th century, cochineal became one of the most profitable exports from Spanish Mexico to Europe. A separate and highly prized red pigment was vermilion, ground from cinnabar, a common ore of mercury. The Romans quarried cinnabar from mines near Almaden, southwest of Madrid. Work there was so lethal because of mercury's toxicity that being sent to those mines was treated as a death sentence; the workforce consisted of slaves and prisoners. The 19th century introduced the first synthetic red dyes, eventually replacing the organic sources that had driven centuries of trade, war, and exploitation.

• 4. Red and Revolution

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  During a strike by English dock workers in the late 18th century, a red flag was carried as a rallying symbol, and the gesture attached itself permanently to the labor movement. In Paris in 1832, working-class demonstrators carried a red flag during the failed June Rebellion, an event later made famous in Les Miserables. The flag was proposed as France's new national banner during the 1848 revolution, but was rejected at the urging of the poet and statesman Alphonse Lamartine. It reappeared as the emblem of the short-lived Paris Commune in 1871. Karl Marx and the European movements of socialism and communism then adopted it. Soviet Russia raised the red flag following the Bolshevik Revolution in 1917, and it flew over that state for the entire history of the Soviet Union. The People's Republic of China adopted its own red flag after the Chinese Communist Revolution. Under Mao Zedong, the Communist Party's anthem became "The East Is Red", and the sayings of Mao were distributed as a little red book in hundreds of millions of copies. North Vietnam adopted a red flag in 1954, and all of Vietnam followed in 1975. The irony that reversed this association in one country arrived in the United States around the 2000 presidential election: after the 39-day recount that followed, media coverage consistently assigned red to Republican states and blue to Democratic ones, a usage that has held ever since.

• 5. Red in Ritual and Belief

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  In ancient Egypt, red was the color of life, health, and victory. Egyptians painted themselves with red ochre at celebrations, and Egyptian women used it as a cosmetic to redden cheeks and lips. Roman generals had their entire bodies painted red to honor a triumph. Roman soldiers wore red tunics, officers a cloak called a paludamentum, and the vexilloid of the Roman Empire displayed a red background behind the letters SPQR in gold. In the Roman Catholic Church, cardinals have worn red since 1295, symbolizing the blood of Christ and the sacrifice of martyrs. Red is the liturgical color for the feasts of martyrs, and it is worn during Pentecost, Confirmation masses, and at funeral masses for bishops, cardinals, and popes. The Shinto tradition of Japan paints the gateways of temples, called torii, in vermilion red and black; these gates mark the passage from the ordinary world into a sacred space, as do the red bridges in temple gardens. In Buddhism, red is one of five colors said to have emanated from the Buddha at enlightenment, associated with achievement, wisdom, and virtue. In Chinese folk religion, red represents yang, prosperity, and good fortune, which is why temple walls, pillars, and palace gates have historically been painted red across the country.

• 6. Dominance, Warning, and Attention

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  In mandrills, the redness of facial coloring is greatest in alpha males and diminishes in lower-ranking individuals, correlating directly with testosterone levels. Studies show that humans who wear red in competitions tend to be judged as more dominant and more likely to win, with judges of tae kwon do having been documented favoring competitors in red protective gear over those in blue. Yet the same color that boosts perceived dominance actually impairs performance when people are placed in achievement contexts, such as taking an IQ test, where exposure to red has been shown to decrease scores. Red became the international color of stop signs and traffic lights under the Vienna Convention on Road Signs and Signals of 1968. That document also standardized red for danger warning signs, give-way signs, and prohibitory signs, following earlier German-type signage established in 1927. Red's reach in signaling extends from bullfighting capes to international football's red penalty card, which disqualifies a player from the remainder of the game and forces the team to continue with one fewer player. Rwanda removed red from its flag after the Rwandan genocide specifically because of the color's association with blood, making it one of the few nations to explicitly break the link.

• 7. Red in Language and Everyday Life

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  Red hair occurs naturally in approximately 1-2% of the human population globally, rising to 2-6% among people of northern or western European ancestry. The gene responsible sits on chromosome 16, where a recessive mutation in the MC1R protein causes the elevated levels of pheomelanin that produce shades ranging from deep burgundy through burnt orange to bright copper. The word "redhead", recorded in its original form as "redd hede", has been documented in English since at least 1510. The language surrounding red runs far deeper than hair color: to "see red" is to feel uncontrollable anger; a "red-letter day" traces to the medieval practice of printing saints' days in red ink in calendars; and "red tape" originated with the English and government lawyers who tied important documents with red ribbon, a practice criticized as bureaucratic excess by the writer Thomas Carlyle in the 19th century. The phrase "red herring" comes from the practice of dragging a pungent smoked fish across a trail to distract hunting dogs. Allura Red AC, the most common synthetic red food coloring today, was originally derived from coal tar and is now mostly made from petroleum. It is banned in Denmark, Belgium, France, and Switzerland, and was banned in Sweden until that country joined the European Union in 1994. On the 30th of June 2010, the Center for Science in the Public Interest formally petitioned the FDA to ban Red 40, and Red 3 dye was banned in the United States in 2025.