Priests in purple robes-purple
The beautiful purple robes worn by these priests deonote them as people of high standing. (Photo source: iStock Photo)

This is a story about color. More specifically, it is the history of two particular colors: purple and blue. I think you will find it fascinating. But first, let’s start our journey with a story of what piqued my interest in the topic.

Purple in Peru

A few years ago, when my wife and I were traveling in Peru, we visited the village of Chinchero, high in the Andes. We stumbled on a weaving shop where you learned how the area’s alluring textiles were made.

We stood, watching five squatting Quechua Indian women. They were artists, weaving Andean llama, alpaca, and vicuña wool into dazzling fabrics famous for their vivid hues and striking designs.

As I watched them work their magic, I wondered, where did these vibrant pigments come from? We drew closer to see the details. The women placed a small heap of grayscale insects, called cochineal (pronounced co-chee-kneel), they had collected by hand from prickly pear cacti. One woman crushed the pile of insects with a pestle. Another poured some wood ashes on their pulverized bodies.

We gasped – the ashen powder turned red, then red-purple, and finally a radiant blue-purple.

weaver of Chinchero making dye for colors purple and blue
A weaver of Chinchero showing us how she makes dyes. (Photo by P.Salber)
I closed my eyes, recalling the wonder I felt in elementary school when the teacher demonstrated the litmus test. We had just witnessed an elaborate experiment carried out not by chemists in their laboratory but by people who are one with their environment and are living its most intimate secrets. Whether they understood the molecular basis of the change, as laboratory chemists would, was irrelevant.

How on earth did they figure this out?

As my kids would say: AWESOME! Envision the Quechua learning that these insects produce color. Crushing one of them between your fingers stains them a bright red. The bodies of the dried female insects contain 12-16% carminic acid which is a vivid shade of crimson.

But, how did they learn to combine different additives to the crushed dried bodies of these insects in order to create different shades of the original color? They likely experimented, as scientists do in their laboratories.

Wood ash and other alkaline substances increase the pH of the mixture to create purple. Small amounts of iron can also be used to transform the red to purple. Adding an acid, such as lemon juice, produces a bright scarlet. This brings me back to my wonder when I learned of the litmus test.

The surprising role of the colors blue and purple in history

  • The ancients knew how to make the colors purple and blue

    • As early as 3000 years ago, the ancient Phoenicians made three major discoveries:
        • They gave us the alphabet we are using today.
        • They discovered that by heating silicon oxide, found in unlimited quantities in the sands of the Mediterranean beaches, they could make glass.
        • And, by extracting the secretions of the seashell Bolinus brandaris (also called Murex brandaris) found on the beaches of the eastern Mediterranean, they could make a highly-prized purple dye. The dye did not fade with time but instead increased in brilliance with exposure to air and sunlight.

The dye was called Tyrian Purple, after the Phoenician port city of Tyre. They also extracted another dye, Royal Blue, from a closely related species.

As we’ll see later, the process of getting the blue dye was not straightforward and was very laborious. Couldn’t the ancients find an easier way to get blue?

As Baruch Sterman, a physicist in Israel, explains that our eyes can only see an object as blue when it absorbs red light. This is something few naturally occurring materials do.

Stones and plants were among the handful of naturally occurring blue materials in ancient times, including:

        • stones, including lapis lazuli from what is now Afghanistan
        • plants such as indigo that grow in warm climates like India and Africa
        • woad  (a plant of the cabbage family) that grows around the Mediterranean.

Ground-up lapis lazuli can be used to make paint, but not to dye textiles. Sadly, while indigo and woad dye fabric, they eventually fade.

Part of what made murex dye so valuable was that its colors remain brilliant. For example, 2,000-year-old pieces of murex-dyed wool found in caves near the Dead Sea are still vibrant today [REF]. Unlike the Andean women we observed in Chinchero, there are no Phoenicians around to explain how they did it.

Enter the archeologists 

An article in the journal, Archeology, describes new evidence of a robust dye industry that endured on the Mediterranean coast for millennia. A dig in Tel Shikmona, south of the city of Haifa in Israel, yielded dozens of pottery vessels and shards covered with purple and blue stains. They also unearthed industrial pools and mounds of murex shells.

Some aspects of the process of dye-making are currently unknown. However, we do know that it involved breaking open sea snail shells, removing the hypobranchial gland, and harvesting the clear fluid inside. In a process that took several days, this liquid was then heated and dissolved in an alkaline solution believed to have been made from urine or certain plants. This eventually produced a yellow fluid, into which yarn was dipped. Upon being exposed to light or oxygen, the yarn turned a rich shade of purple.

Extraction was tedious and inefficient. Thousands of Murex shells were required to dye just one Roman toga. The Phoenicians demanded a very high price for these precious goods. Their fabulous profits led to resentment. They were considered gougers and thieves. However, we now know that the traders were simply reacting to the reality of supply and demand. They had, after all, cornered the market.

The color purple was reserved for royalty

Because the purple stuff was so expensive, only kings and emperors could afford it. They allowed senators to have togas with a stripe of purple, but that was it. Commoners could only wear white, or earth tones like brown or green.

In fact, sumptuary laws were passed that regulated who could wear what. These laws were ostensibly designed to avoid conspicuous consumption. In reality, they fixed the demarcation between the aristocracy and the rest of us (assuming, dear reader, that you are not an aristocrat).

As a consequence (not completely unintended), these laws limited the demand for these sumptuous dresses, keeping the price more affordable for the nobles, and away from the hoi polloi.

Mosaic of Justinian in purple robe
This beautiful mosaic from Basilica San Vitale shows Justinian in all his purple glory. (Photo by Petar Milosevic CC BY SA-4.0 via Wikimedia Commons)

After the sack of Constantinople in 1204 by the crusaders whose stated mission was to liberate Jerusalem, rather than the reality of plundering the capital of the Christian Byzantine Empire, the impoverished Byzantine emperors could not afford the glorious purple dye anymore.

Later, medieval kings and fabulously rich Popes (who weren’t sworn to poverty at the start of their ecclesiastical careers) adorned themselves with Tyrian purple dresses.

The Church also controlled the message by paying its favorite artists de jour quite handsomely to tell the stories of the Bible through art. So only the artists close to the trough could afford the brilliant purple dye. And the message? Only the VIPs, such as Jesus, Mary, and some favorite kings merited Tyrian Purple. 

And so it went until the 18th century and the Age of Enlightenment when liberal and democratic ideals swept away the symbols of Church and State hierarchy. About this time, chemistry began producing brilliant pigments affordable by the new middle class.

More articles from the author:  
The Fascinating History of the Color Red
Science Shines a Light on the Evolution of Music and Language

The evolution of color recognition throughout history

While you may not remember all of the details of the Iliad and the Odyssey, you may recall Homer’s enigmatic description of the “wine-red sea.” Wine-red? Has anybody ever seen the sea in anything even remotely resembling this color?

Could the famous blue of the Aegean Sea, where the Homeric events took place, ever be other than brilliant blue? Literary scholars struggled mightily with this strange depiction. Some attempts were so convoluted as to be laughable, but none were persuasive.

To compound the mystery, the colors red, black, and white are mentioned many times in the ancient manuscripts. In the later ones, such as the Bible and the Koran, green and yellow are mentioned as well. In fact, biblical red is described in many of its hues (“argaman”—dark red, just like Homer’s sea, “shani”-pink, “siqrah”-deep red). And so is green: olive green, grass green.

But not a hint of blue. 

William Gladstone, a famous British prime minister at the beginning of the 20th century, was a classical scholar. He published a 1700-page study of Homer’s epic poetry. In a 30-page chapter, he describes Homer’s strange choice of colors – sheep wool and ox skin as purple, honey as green, horses and lions as red. The sky is studded with stars, wide, having an iron or copper hues. Not one mention of blue.


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What’s neurobiology got to do with it? 

Scientists believe that the historical mislabeling of colors (by today’s standards) is not just a simple case of nomenclature. When we get used to seeing two hues as different colors, language trains us to see them as different entities. And the brain then exaggerates these differences, especially at the border areas between them.

Everyone is a bit different in how they perceive and call out the name of colors.  I see red in many hues – dark red or light red. My wife sees peach and orange and strawberry as distinct colors

Blue, which we perceive as lighter and totally distinct from black, is in reality probably a bit darker and closer to black. The “obvious” distinction between black and blue is a figment of our imagination. Modern neurobiological research provides ample evidence for that.

Why were black, white, and red the first colors to be perceived by our forefathers?

The evolutionary explanation is quite straightforward: Ancient humans had to distinguish between night and day. Red is important for recognizing blood and danger. Even today, the color red causes an increase in skin galvanic response, which is a sign of tension, and alarm.

Green and yellow entered the vocabulary as the need to distinguish ripe fruit from unripe, grasses that are green from grasses that are wilting, etc. What is the need for naming the color blue? Blue fruits are not very common and the color of the sky is not vital for survival.

Stay with me. First, here is a totally unexpected phenomenon: language influencing brain function. But even more fascinating is the realization that the way we see the world is somewhat of an illusion. It is a product of a trick played on us by none other than our own brain.

This brings us full circle to the ancient Greeks and Plato’s allegory of the cave. He posited that reality is an illusion. It is like the shadows of cave dwellers cast on the walls of a cave by a fire at the cave’s opening. We, standing outside the cave, see the shadows only, not the real occupants.

Reality, as we see it, is illusory.

Mind-boggling.

How pigments are used in medicine

With the democratizing effect of chemistry-for-the-masses came another revolution: the Biology Revolution. It was an exhilarating time for people curious about the inner workings of living things:

      • The microscope allowed scientists to view cells for the first time.
      • The electron microscope allowed them to see the innards of the cell.
      • Pathologists could stain tissues, depending on their surface charge, with either a blue dye (hematoxylin) or a red one (eosin). 
      • To increase the staining specificity beyond just surface charges, researchers developed antibodies to specific cell types, like lymphocytes or muscle cells, or neurons, and bound them chemically to various dyes.

Now they could visualize exactly how the heart muscle is organized, how one lymphocyte type differs from another, and how neurons are organized in the brain.

As important as this pigment revolution was, it had a major shortcoming. It only showed the cells as static objects. In biology, nothing is static. Cells move within tissues and all around the body. Inside the cells, there is a constant flow of proteins and organelles performing their duties.

For many years, researchers could only speculate on what’s happening inside the cell, based on visual cues. But then a quantum jump occurred in the development of pigments that made tracking of cell components inside the cell possible.

The discovery of green fluorescent proteins wins a Nobel Prize

The discovery of green fluorescent protein (GFP) in jellyfish spawned such an impressive revolution in cell biology and medicine that its discoverers, Martin Chalfie, Osamu Shimomura, and Roger Y. Tsien were awarded the Nobel Prize in Physiology and Medicine in 2008.

Here are some short quotes from the Nobel committee: 

“To obtain such knowledge (of the dynamic behavior of cells), new experimental and conceptual tools were required. Now, at the beginning of the 21st century, we are witnessing the rapid development of such tools based on the green fluorescent protein (GFP) from the jellyfish Aequorea victoria, its siblings from other organisms, and engineered variants of members of the “GFP family” of proteins.

Indeed, no other recent discovery has had such a large impact on how experiments are carried out and interpreted in the biological sciences, as witnessed by the appearance of more than 20,000 publications involving GFP since 1992”.

To close the loop, a paper published in the May 2008 issue of Genetics announced the discovery of a new Purple Fluorescent Protein. Now we can track simultaneously many proteins and organelles as they course through the cell. Some stain green, some blue, some red, and yes –some stain a brilliant, majestic purple – a ballet in astounding colors.

The story continues: A new blue is invented

At the time of the discovery of YInMin blue, it had been more than 200 years since a new inorganic blue pigment was created. The last being the discovery of cobalt blue in 1802. Oregon State University materials science professor, Mas Subramanian, inadvertently created it while searching for inorganic materials that could be used for electronic devices.

He put a sample containing manganese, yttrium, and indium (thus the name) in a very hot furnace (more than 2,300 degrees Fahrenheit) and was surprised to find it turned a “brilliant, very intense blue.” Dr. Subramanian noted that this color was a “true” blue as opposed to many blues in nature that appear blue because of the way they reflect light. 

Also, because it is chemically derived as opposed to being an organic plant-based dye, this intense blue color should remain stable over time. This blue already has widespread applications in a number of industries, including commercial paints for buildings, fashion, art, and even cosmetics.  

Concluding thoughts

The history of the colors purple and blue goes beyond amazing. It is a metaphor for the eternal struggle between the haves and have-nots. Originally the pigment was so expensive so as to only be afforded by kings, emperors, and the church hierarchy.

These powerful people passed laws ostensibly to prevent conspicuous consumption. In reality, these sumptuary laws were designed to restrict competition for the pigment. Thus, ensuring lower prices for themselves.

With the dawning of the enlightenment and the empirical science of chemistry that it gave birth to, the pigment purple became affordable to the masses. These dual triumphs of democratization and the flourishing of technology resulted in the totally unforeseen explosion of knowledge applied to the understanding of our biology and the development of modern medicine.


First published 5/5/11.

Dov Michaeli, MD, PhD

Dov Michaeli, M.D., Ph.D. (now retired) was a professor and basic science researcher at the University of California San Francisco. In addition to his clinical and research responsibilities, he also taught biochemistry to first-year medical students for many years.

During this time he was also the Editor of Lange Medical Publications, a company that developed and produced medical texts that were widely used by health professionals around the world.

He loves to write about the brain and human behavior as well as translate knowledge and complicated basic science concepts into entertainment for the rest of us.

He eventually left academia to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early-stage biotech company that developed products to improve post-surgical pain control.

Now that he is retired, he enjoys working out for two hours every day. He also follows the stock market, travels the world, and, of course, writes for TDWI.

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