Image (cropped): Benh LIEU SONG [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Blue birds, blue jays, cerulean warblers, peacocks: all blue birds, but none of them are actually blue. There are no known bird species that produce blue-pigmented feathers (and in fact, only a very small handful of vertebrates are capable of making a blue pigment). The color we perceive these birds to be is due to the structure of their feathers, which reflect light in a way that makes them appear blue. The same is true for the scales of the brilliant blue morpho butterfly, the shells of certain beetles and even blue human eyes. 

But what is “actually” blue, anyway? Is there such a thing? To answer that, we have to explore the very nature of color: what it is, how we perceive it and how we use it.

Close-up image of blue morpho butterfly next to a photograph of a peacock's head and neck
Blue morpho butterfly Image: Gregory Phillips [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)] | Peacock Image: fir0002 flagstaffotos[at]gmail.com Canon 20D + Canon 70-200mm f/2.8 L [GFDL 1.2 (http://www.gnu.org/licenses/old-licenses/fdl-1.2.html)]

What is Color?

Since the Earth began its dance around the sun, it has received energy from the star in the form of white light. Light is a wave, its motion the same as a wave in the middle of the ocean. Picture a boat at sea, bobbing up and down as the waves roll by. Light waves follow the same motion; however, their movement is imperceptible, because their undulation clocks in at about 400 million million times per second — and this is just the part of the spectrum we can see. “Color” is this visible spectrum of light, and each hue is defined by — and due to — its frequency, from red (the lowest, longest of the visible frequencies), through orange, yellow, green, blue and indigo to violet (the highest, shortest visible frequency).

Illustration of light entering a prism and exiting as a rainbow
Light enters a prism and exits as a rainbow. Image credit: Suidroot [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
 

Around 1665, Isaac Newton directed light through a prism onto a wall and watched a rainbow bloom on the plaster. This observation led to a better understanding of light and color. We now know that white light from the sun (or a lightbulb) is composed of all colors. When these lightwaves strike an object, the apparent color of that object is a result of the color frequencies it absorbs and/or reflects. For example, a white sheet of paper reflects all colors, resulting in a white appearance. A red apple absorbs all color frequencies except for red, which is the color we perceive it to be. A black stone absorbs all color frequencies, reflecting none — and so we perceive it as black. The energy these colors are carrying is turned into heat; dark objects absorb this heat along with the color frequencies, which is why they feel warmer in the sun. 

So do objects have color in the dark? This question may seem like a meditation puzzle, similar to the old koan “What is the sound of one hand clapping?” But think about it: if color is a result of lightwaves, and there are no lightwaves in the dark, does an object in a darkened room have a color? 

How Do We Perceive Color?

For millions of years, we did not register color at all…because we didn’t have eyeballs to view the light. Around 500,000 years ago, single-celled organisms like the Euglena developed light spots, or clusters of light-sensitive proteins, to find and make food. Over time, we evolved eyes capable of processing light and color and brains capable of interpreting this information.

Humans see due to two kinds of photoreceptors in our retina: rods and cones. Rods are responsible for vision in low light levels, like nighttime, a darkened room or the recesses of a cave. Cones are responsible for color vision; the typical human eye has three types of cones, each able to process a different wavelength (red, blue and green). The retina also contains nerves, which communicate to the brain what the photoreceptors see; the brain then takes this color information (i.e., which cones are stimulated) and translates it into color.

Television monitors and smartphone screens work in much the same way. If you get very, very close to a screen, you will see it is composed of rows and columns of dots, called pixels. Each dot contains three colors: red, green and blue. The colors within each dot are turned on or off in combinations to reproduce the entire spectrum of colors. 

Why Do Colors Matter? 

Why did we evolve to see in color? Well, color is useful in myriad ways: it provides camouflage for owls, octopi, caterpillars, lizards and a host of other creatures; it helps animals like the magnificent frigatebird to attract mates and flowers like the blackeyed susan to beckon pollinators. It delineates tasty food like berries and even serves as a warning, such as the vibrant skin of poison dart frogs or the green tinge of spoiled meat.

A close-up photo of a male magnificent frigate bird, with red neck pouch inflated to attract a mate
A male magnificent frigate bird hoping to attract a mate. Image credit: Forest and Kim Starr, CC BY 3.0 us, https://commons.wikimedia.org/w/index.php?curid=71969416

As humans evolved, so did our language of color — both literally and metaphorically. The majority of languages around the world follow the same trajectory with regard to color: they begin by differentiating between light and dark, then they give red a name. Over time, they name yellow and green, then blue and brown, and eventually pink, purple, orange and gray. 

Experts believe that colors were named in this order because light and dark were most central to their lives; red was everywhere, both in their bodies (in the form of blood and flushed or sunburnt skin) and the outside world (fire, the blood of animals, the earth they tread); then came the green and yellow of living things — of grass and edible plants and the shady canopy of trees. Next was the clean, cool blue of a clear sky and fresh water and tracks in new-fallen snow; then the deep brown of the soil they tilled and planted, the muted browns of hare and deer they hunted and nuts they foraged. The rest, relatively rare in comparison, came later. 

What Do Colors Mean to Us?

Like an Impressionist’s canvas, our interpretation of colors is layered and difficult to delineate. First, there is a base layer composed of a primal sense of what colors mean: darkness, daylight, food, companionship, feelings of calm or danger. Then, the canvas is painted again and again by different cultures at different times. One color may symbolize many things — some contradictory — in even a single culture. 

Take red for example — the color used in 77% of flags around the world. It’s a dynamic color; red seems to move toward the viewer, as opposed to blue, which seems to recede. Red is attention-grabbing, and therefore used in stop signs and fire trucks…and also red-light districts. Red is associated with power, anger and violence, but also passion, love, and in some cultures, good luck and happiness. 

Yellow is the most visible color on the spectrum, and therefore used in school buses, caution signs and traffic lights — but it also conjures joy and sunshine. Blue is peaceful and calm, but also excellence in a blue ribbon, sad with “the blues,” and authority in police uniforms, military dress blues and the blue blood of the aristocracy; perhaps this is why blue is the most commonly used color in corporate identity. Green is envy, luck, inexperience, but also growth and renewal and the color (and verb) of a global movement to take better care of our planet. Color has been used in various ways to divide us, but rainbows often symbolize unity.

How Do We Use Color?

Color must have seemed like magic long ago, when brilliant hues were found only in nature. We first daubed pigment on cave walls around 15,000 BCE, using a limited palette of white, black, reddish and yellow ochres. There is some evidence that we began dyeing textiles in the Neolithic Age, around 10,200 BCE, using iron oxide pigment, and in China, dyes derived from plants, bark and insects have been traced back 5,000 years. 

Cave paintings at Laas Geel near Hargeisa in Somaliland/Somalia
Cave paintings at Laas Geel near Hargeisa in Somaliland/Somalia, estimated to date between 9,000 and 3,000 years BC. Image credit: Abdullah Geelah [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]
Some dyes were plentiful and easy to use; others, such as Tyrian purple, were the opposite. This special purple was made from two varieties of shellfish, and the manufacturing process was complicated and pretty disgusting. The gastropods produced only a single drop of liquid each, and it took 250,000 of them to make an ounce of dye. In ancient Rome, the color became a badge, marking out generals, senators and emperors; however, by the fourth century A.D., only the emperor could wear purple, and anyone defying this was subject to death. This is a strong example of sumptuary law, a concept created to keep common folk from imitating royalty or purchasing luxury goods, and in some cases, to keep citizens in line with religious teachings. 

In 1856, a teenaged scientist named William Henry Perkin attempted to synthesize the malaria treatment quinine from coal tar and accidentally advanced the field of chemistry. His failed experiment left an oily residue behind in the beaker. Curious, he dipped a length of silk in the gunk and was amazed to find the fabric dyed a brilliant purple, which he named mauveine. Suddenly, brilliant color was easier to achieve—and cheaper, with a rainbow of dyes now available to the masses. His discovery not only democratized color, but also paved the way for developments in photography, perfume, medicine, explosives, plastics and photography. 

Want to Learn More?

The Wilson College of Textiles is proud to be home to leading color science researchers and dyeing and finishing experts, including David Hinks, dean of the Wilson College of Textiles; Ciba Professor of Textile Chemistry Renzo Shamey; Nelson Vinueza, associate professor Department of Textile Engineering, Chemistry and Science (TECS); and TECS professor Harold Freeman. Through our Polymer and Color Chemistry program (PCC), students can learn about sustainable dyeing, human color perception, dye-sensitized solar cells and more. They also have access to impressive collections and state-of-the-art facilities such as the Max Weaver Dye Library (donated by the Eastman Chemical Company), the Dye Synthesis Laboratory and the Datacolor Color Science Laboratory and the Optics and Imaging Laboratory

Students can explore color in other ways through the Department of Textile and Apparel, Technology and Management (TATM), such as the use of color in brand images and retail experiences, complementary colors in fashion and textile design, and hand dyeing with natural pigments. 

Through our World of Color series, over the next 12 months, we will be exploring many facets of  color, including the sometimes surprising history of natural and synthetic dyes, photodynamic cancer therapy, color in cosmetics, amazing advancements in solar collection and storage, the building blocks of dye, how Pantone picks its colors, and so much more.

 

Follow the Wilson College of Textiles:

Twitter: @NCStateWilson

Instagram: @NCStateWilson

Linkedin.com/company/nc-state-wilson-college-of-textiles/

Facebook.com/NCStateWilsonTextiles/

 

Further reading: https://textiles.ncsu.edu/news/2018/11/nc-state-library-where-hair-product-researchers-go-to-dye/