Indigo & Isaac Newton

Indigo was included in the color spectrum by Isaac Newton because he wanted the spectrum to have seven colors instead of six.

Isaac Newton’s pioneering experiments with light & prisms explained how white light is actually the combination of several wavelengths (colors) of light. He demonstrated this using a prism to break apart white light into its composite colors and then used a second prism to recombine those colors back into white light. When white light is broken apart the “spectrum” (a word Newton introduced to the field of optics meaning a “continuum of color”) has many colors. Exactly how many colors is open to cultural interpretation.

Isaac Newton refracting white light through a prism, demonstrating that white light is comprised of more than one wavelength of color.

Any Color You Like

Most human eyes are essentially the same which means that most of us are physically capable of seeing & differentiating all of the same colors. Where we differ is how we think about color. Your culture & language influences how you categorize colors.

The importance of, and names for, different colors varies from culture to culture. For example, the medieval English didn’t have a name for the color orange until the 16th century, so before then things that were orange were just called red (like “redheads” and the robin “redbreast”). It’s not that they couldn’t see orange, they just didn’t have a name for it because having two distinct names for red and orange wasn’t important until then. Russian, Greek, Turkish, and Hebrew all have two different words for idea of blue: one for darker blue and the other for lighter blue.

Hungarian has two different words for red depending on what you’re describing. “Piros” is used for red inanimate objects or red cheerful things, while “vörös” is used for red animate things or red serious things. Irish Gaelic has two words for the idea of green depending on where it’s seen. “Glas” is used for the green of plants while “uaithne” is used for the green of artificial dyes. The hue of a plant and a sweater could be exactly the same, but in Irish Gaelic different words will be used for the idea of green. In a nutshell: the names, categorization, and importance of various colors is entirely influenced by which culture we are a part of.

This cultural influence also applies to the spectrum of color and rainbows. Illustrations of rainbows contain discreet, countable, bands of colors. In nature however they’re continuous gradations of wavelengths/colors. Assigning a fixed number of colors to a rainbow depends on your cultural interpretation. In Islam, rainbows traditionally only have 4 colors corresponding to the four elements of water, earth, fire and air. Western culture should probably only have six colors, but we have seven because of Isaac Newton’s interest in mysticism.

Isaac Newton included seven colors in his spectrum because he felt the number seven was mystical & important. To do this he selected one tertiary color, indigo, to be included in his list of colors.

The Sacred Seven

As scientifically minded as Newton was, he also held occult/mystical beliefs. He believed in sacred geometry and the ideas of Pythagoras that there was an importance to the number seven. At first, after refracting white light, Newton recorded observing five colors (red, yellow, green, blue, violet). Then he recorded seeing six (he added orange). But to Newton six wasn’t as satisfying as seven. There are seven notes in the western major scale, seven days in a week, seven known “planets” in the sky (in Newton’s time), but only six colors in the spectrum of light? This wouldn’t do, so he added indigo.

The first six colors he observed are a logical western division of the spectrum:
• three primary colors (red, yellow, blue)
• three secondary colors (orange, green, violet)

Indigo is a blend of blue + violet and as such is the only tertiary color he included. It’s not that indigo isn’t part of the spectrum (it’s definitely there), but rather the problem is that it’s the only tertiary color listed because Newton shoehorned it in. Why indigo? Why not vermillion or cerulean? Indigo’s inclusion was an arbitrary choice driven by Newton’s desire to have seven colors instead of six so he picked one tertiary color but ignored the five others. Cultural influences pushed him to find seven colors instead of six (or eight, or twelve, or any other number). Centuries later we still divide the spectrum into seven colors because of Newton.

Eye Color

Humans originally had brown eyes until genetic mutations started making variations. No two eyes are identical, not even your own.

Your eye color & design is as unique as your fingerprints. Several gene variations all contribute to giving each of your eyes a particular design and shade of color (or colors plural if you are heterochromatic) that nobody else has. Not even your own two eyes are identical. Originally all humans had dark brown eyes (along with dark brown skin) which helped to reflect some of the harsh rays from the sun. As groups of humans migrated out of Africa and up into Europe, where there are seasons with less sunlight and the land is further away from the direct sunlight of the equator, there was no longer a need for so much protection from the sun’s harmful UV light. This is where the first mutation in human eye color took place. Sometime between 6,000 and 10,000 years ago the first blue-eyed person was born, from which all other blue-eyed people are descendant.

Eye Colors

Our skin and hair is colored using the brown pigmentation called melanin. The back of our irises also contains melanin which gives our eyes color. Melanin is brown, and so brown eyes using brown pigmentation is easy to understand. Light enters the iris, the melanin absorbs some wavelengths of light and reflects back out the necessary waves to make the color brown, making brown eyes brown.

You would think then that blue eyes use blue pigmentation, but they don’t. Blue eyes use the same brown pigmentation as brown eyes but in lesser quantities. The other trick is that, since eyes are three dimensional, blue eyes absorb and scatter waves of light differently than brown eyes. The longer light wavelengths (reds & oranges) get broken up inside the eye and only the shorter wavelengths (blues) get reflected back out making blue eyes look blue. This scattering effect of allowing/blocking certain wavelengths is also what gives the sky color.

Even though all colors of eyes use brown melanin, variations in the construction of the eye and how it absorbs & scatters various light waves makes an iris a certain color.

Brown, blue, gray, hazel, green – all eye colors use some amount of brown melanin combined with various ways of scattering & absorbing light to make whatever color the eyes are. Depending on the severity of their condition, humans with albinism can lack the necessary pigmentation to make their irises as opaque as other people’s. Irises that fail to block excessive light from entering the retina can cause a variety of vision problems including extreme sensitivity to bright light.

What does eye color “do”?

As for any potential purpose, eye color doesn’t “do” much. Unlike other genetic traits which evolution embraced because they helped our chances of survival, eye color variations seems to be largely perpetuated through romantic desirability. People find certain eye colors more attractive and so the genes for those colors live on. Your eyesight isn’t any better or worse because of a certain color eyes. Light travels through the pupil to the retina and so the color of the iris doesn’t change what you see. This is why cosmetic contact lenses can change your eye color without changing what you are seeing – they are only covering the iris.

There are some minor effects of having different eye colors. Because of how light is scattered and absorbed inside the eye, lighter colored eyes are sometimes more sensitive to bright light leaving some to squint more as well as needing to wear sunglasses more frequently. Driving at night can also be difficult because the glare from oncoming traffic can be more harsh. People with light colored eyes are more likely to develop macular degeneration, but people with brown eyes are more likely to develop cataracts. Finally, people with light colored eyes tend to perform better in sports where they control the hand-eye coordinated action such as in bowling, golfing, pitching, etc. Brown-eyed people tend to be better at sports where they react such as hitting a ball, boxing, playing defense, etc.

Added info: Getting reliable statistics on eye colors is difficult. That said brown eyes are the most common color type in the world at somewhere between 55-79%. Gray eyes seem to be the rarest at less than 1%. The eyes of some babies start out as blue but eventually become green or brown as their eyes develop more melanin. Few blue-eyed babies will have blue eyes as adults.

Liz Taylor was said to have violet eyes, but in reality she had blue eyes but with a genetic mutation to have double eyelashes which made her eyes look more purple. David Bowie was known for having two different colored eyes, but this was also an illusion. When he was 15 he got in a fight over a girl and his left eye was damaged leaving the pupil permanently dilated. This gave the impression that he had one black eye and one blue eye, but in reality both of his eyes were blue.

Liz Taylor and David Bowie both had remarkable eyes.

Fade to Black … and Blue

Printed materials fade to black and blue because black and cyan ink are more resistant to the sun’s short UV waves

When you have a poster, a newspaper, or some other printed material sit in direct sunlight, the colors fade over time and frequently you are left with a mostly black & blue print. Colors fade for a variety of reasons (humidity, the type of paper, the types of inks, the temperature, etc) but exposure to light, and in particular ultraviolet light, is the primary reason.

The electromagnetic spectrum accounts for photons with a variety of wavelengths – from the very short (gamma waves) to very long (radio waves). The portion of the spectrum we can see with our eyes is known as visible light, which accounts for all the colors of the rainbow. Blues and violets are shorter wavelengths than yellows and reds. Sitting just beyond the blues & violets is ultraviolet (UV). While blue and violet are visible, ultraviolet is invisible. UV wavelengths are just a bit shorter than what our eyes can perceive. UV wavelengths are also dangerous.

When ultraviolet waves from the sun hit printed materials their short wavelengths can break the chemical bonds of the colored inks. The more damage to those chemical bonds the less those printed colors are able to continue reflecting the wavelength of their particular color. The typical printing process uses 4 colors: cyan, magenta, yellow, and black. Cyan (blue) reflects the relatively short wavelengths to make the color blue and as such it is better equipped to resist the even shorter wavelengths of UV. What we see as “black” is frequently a dense combination of ink colors (including black ink) and so it takes longer for this combination of inks to fully breakdown (although it will start to shift and lighten in color). Yellow and magenta however are forced to absorb shorter wavelengths and only reflect the longer wavelengths that are their colors. As such, the yellow and magenta in a printed poster tend to fade faster because more ultraviolet light is being absorbed and breaking down the chemical bonds of those inks.

This is why printed materials sitting out in the sun for too long will commonly lose their warmer colors faster than their black and blue colors.

Added bonus: The Earth’s atmosphere blocks a lot of UV waves from the sun, but some still enters our atmosphere. Because the moon’s atmosphere is too weak to block the sun’s ultraviolet waves, the American flags planted on the moon are all white at this point after decades of ultraviolet exposure has faded all of their colors away.

White Hats & Black Hats

The heroes and villains in westerns had reliable looks

In old black & white westerns of the 1920s-40s, the heroes and the outlaws generally followed pretty standard looks. Our heroes would be in white hats, our villains in black hats. This is largely because of (geographically) western culture’s semiotic associations that the color white represents good while the color black represents evil. Also, white & black standout more in the colorless mediums of early movies and tv. The show Westworld carries this forward when visitors to the park choose which color hat they want, which informs their experience in the park of being a good guy or bad guy. This distinction of white hat or black hat has become a metaphor more broadly for good guy or bad guy. In the hacking community white hat hackers hack ethically in order to find security flaws and work with companies to improve their defenses, while black hats villainously hack to steal information.

Beyond just how they look, some westerns also had the heroes and villains move in certain directions during pivotal scenes. Because most people are right handed, heroes would walk from left to right across the screen with their gun hand visible to the viewer, keeping their intentions known at all times. Villains would approach from right to left, with their gun hand hidden from the viewer, as if hiding their intentions from the audience.

Outside the western

Our association of black hats and villains extends beyond tv & movies. A study of 25 seasons of NHL hockey found that players wearing black are penalized more frequently than players in lighter colors. Whether the players in black really are more villainous and commit more penalties or just that the referees are biased by black clothes and think the players to be more villainous and probably deserving of more penalty time, is unclear.

One notable exception with our connotations to the color black is of course is the Man In Black, Johnny Cash, who sang that he wore black as a visible symbol of his solidarity with the marginalized people who our society has ignored & abandoned.

Blue Raspberry

At the confluence of food safety and marketing, blue raspberry was born.

In the natural world, no raspberry is anywhere close to the electric blue shade of “blue raspberry.” Most raspberries are red but there are some blue-ish raspberries. The white bark raspberry, native to western North America, is a very dark shade of blue, nearly black. So why do we have the flavor and color of blue raspberry?

Red Number 2

In the 1950s there was a growing movement in the U.S. to ensure the safety of food and food additives. There was increasing doubt over the safety of the food dye Red No 2 (which at the time was made from coal tar). Food companies could capitalize off of this concern if another color was used.

It was during this time that the Gold Medal company of Cincinnati introduced a new flavor of blue raspberry cotton candy. Blue raspberry’s popularity grew but things really took off when Icee introduced their blue raspberry flavored frozen drink in the early ‘70s. The competition between blue raspberry and red flavored candies/drinks was taken to a new level in 1976 when Red No 2 was banned in the United States because it was potentially carcinogenic. Simple put, at the time, Blue No 1 was safer to consume than Red No 2.


To mimic real life, food companies then and now use the color red for lots of flavors: cherry, apple, cinnamon, watermelon, cranberry, etc. It’s a crowded space. However, there are not many foods that are naturally blue, which as a marketing opportunity was very attractive. Blue was a way to set raspberry apart from the other flavors. This is similar to why pink lemonade exists: lemonade isn’t pink, but it’s a bright color that stands out from the crowd. Blue raspberry had the color all to itself for a long time which was marketing gold.

Orange the fruit, orange the color

Orange the color was named for orange the fruit, not the other way around.

The English word for the color orange has a trail back through a few European languages but has its origins in the Sanskrit “nāraṅga” which was the name for the orange tree. Oranges the fruit came to Europe through Spain with the Moors, who in Arabic called the fruit “nāranj”.

From the Arabic name for the fruit, “nāranj” became “narange” in English in the 14th century and by sometime in the early 16th century the spelling became “orange”, and was then used to describe things that were the color of the fruit.

Some confusion may apply

Without a name for a color, cultures use the words they do have to describe the things around them. Because English didn’t have a word for the color orange until the 16th century, some things that are orange (or orange-ish) were labeled as red because it was the closest color that English had a word for. “Red” hair and the robin “redbreast” for example are really more orange than red, but they were named before English had the word “orange”.

Describing the colors of things before a language has names for those colors had been a problem across cultures for a long time. The Ancient Greeks had a very limited palette of color names to choose from. For example, there seems to have been no word in Ancient Greek for the color “blue” so in Homer’s The Iliad and The Odyssey he describes both the sky and the sea as being a wine / bronze color. Even stranger, he also describes sheep as being wine colored.