The Color Pink Doesn’t Exist? So Why Can We See It?

Melissa 21
pinkAbsent from the visible spectrum and neither a wave nor a particle, the color pink is, for many, a scientific enigma: how can a shade that doesn’t even appear in the rainbow exist? The answer lies in color theory.

The Primary Colors: RGB

Unlike art production (see below), when it comes to eyesight (and video production), the primary colors are red, green and blue.

At the back of your eyeball, sitting on the thin, light-sensitive retina, are millions of rods and cones. The rods (all 120 million) are all the same and each is sensitive, and only responds, to light or its absence. On the other hand, the cones (only 6-7 million) come in three types: red-, green- and blue- sensitive.

Light is both particle and wave, and like other waves, moves at certain frequencies. The visible light we see zips in at about 400 million, million times per second depending on the color. Violet (at one end of the visible spectrum), is the fastest, while red (at the other end) takes its sweet time. The other colors in the spectrum, moving at their particular frequencies, are indigo, blue, green, yellow and orange. The color pink, not a part of this spectrum, does not have a particular frequency.

Now, when light from the Sun hits an object, all spectrum colors are present, although, typically, most are absorbed. The color reflected the most is the color your eye sees. For example, with a banana, every color except yellow is absorbed. When all colors are absorbed, you see black, and when all colors are reflected, you see white.

When light gets to the back of your eye, it hits the rods and the cones. In low light, a tyranny of the majority occurs, and the far more numerous rods take control of your eyesight. As the rods only detect the presence or absence of light, in this situation, your view looks a lot like night-vision goggles.

However, in brighter light, the cones kick into gear and the world becomes more colorful. The three primary colors (RGB) are each typically detected by their respective cones, although green perception may also involve the blue and red cones (which helps explain color-blindness). When it comes to the other colors, though, it is a bit more complicated.

Consider yellow. It exists as a wavelength, but your eye lacks yellow-sensitive cones. In that absence, yellow activates your red and green cones, and, firing together, they send a message to your brain. There, your noggin translates the red and green transmissions into yellow. Likewise, blue cones work with green cones to produce cyan and with red cones to produce magenta.

Sometimes, one type of cone is dominant and a second only partially activates. For example, violet fully activates blue cones, but only half-heartedly works on the red. Both orange and brown, however, have red as the dominant cone type with green only partially activated.

Furthermore, there are colors that require all three types of cones. White occurs when all cones fire completely, while black is perceived when no cones are activated. Grey happens when all three cone types react, but only partially.

Pink (light pink, not magenta) falls into this last category. To be perceived, it needs red cones to fully react, and both green and blue cones to only partially activate.

Notice, however, how many of these colors, including cyan, brown and magenta as well as pink, do not exist on the visible spectrum, yet we perceive them as distinct. It is for this reason that some have opined that color perception is “not actually a property of light or of objects that reflect light [but rather] is a sensation that arises within the brain.”

The Primary Colors: CMY(K)

Unlike eyesight and video production, art and print production’s primary colors are cyan, magenta and yellow. Why? The difference lies in the fact that the former mixes light, while the latter mixes pigments.

Additive vs. Subtractive Colors

The hues created when the eye (or screen) mixes red, green and blue inputs are called additive colors. In this process, light waves can be “optically mixed by being placed closely together, or by being presented in very rapid succession.”  In order to work, additive colors require emitted light from a source like the sun or a television. With manmade additive colors, different combinations of red, green and blue light are fired at a screen. One example might be the vivid red super suits in the movie The Incredibles.

However, not all color we see is the result of addition. Remember that most objects reflect only some light waves and absorb the rest; the colors produced by this reflected light (where part of the visible spectrum has been withheld) are called subtractive colors. For example, the bright hue of a Red Delicious apple, which has absorbed the blue, orange, yellow, green, indigo and violet, is a subtractive color.

Eerily interrelated, CMY are the secondary colors of RGB, and vice versa.

What about Red, Yellow and Blue?

The primary colors of your childhood remain alive and well in grammar school classrooms, but do not provide as great a range of color as CMY(K).

Each color model’s range is limited to its gamut. RGB has the largest gamut of the three and RYB, the smallest. RGB, however, which requires emitted light in order to create its full gamut of colors, is unavailable for print or art production (you try to combine green and red to produce yellow). So, most professionals and vendors have adopted the next largest gamut available, CMY(K) (the “K,” by the way, stands for black).

Back to Pink

Lately, pink has come under fire thanks to Henry Reich and his fun and informative Minute Physics. (Seriously, go subscribe to his channel; it’s awesome. And while you’re at it subscribe to our YouTube channel here. You won’t be sorry in either case.) In a 2011 video on YouTube, Reich “proves” that magenta (what he calls pink) cannot exist, either because it could only exist in space already occupied by radio and gamma rays, among other things, or because magenta is really only the absence of green.

In defense of the color, Scientific American’s Michael Moyer delved into optical science and noted that, given the complicated process of photons and neurons interacting with our cones and brains, all colors could be considered a trick of the mind. He finished with: “Pink is real – or it is not – but it is just as real or not-real as red, orange, yellow, green, blue, indigo and violet.”

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21 Comments »

  1. Will November 14, 2013 at 7:22 am - Reply

    Why does a low-saturation Red (that everyone refers to as Pink) get its own proper name, yet the equivalent colors of the other two hues (Blue & Green) do not?

    In other words, why does a low-saturation Green or a low-saturation Blue not have its own proper name, the way pink does?

    They are only referred to as Light Green or Light Blue.

    What makes “Pink” so special?

    Is the interest, and subsequent purpose of this article, based only on the fact that “Light Red” has a special name?

    I have wondered this for years. If anyone has any insight, please share.

  2. Reggie November 14, 2013 at 12:27 pm - Reply

    I totally disagree with Michael Moyer’s conclusion, which you also provided as the last word in your article.

    In fact, pink does not exist with the same degree of reality as red, orange, yellow, green, blue, indigo and violet.

    The ROYGBIV colors correspond with specific frequency ranges as perceived by humans as distinct. While the boundaries between these colors is a matter of human perception, that these different colors represent distinct frequency ranges is a fact long ago established by science. Pink is a color which is distinct in human perception only. It does not correspond to any single specific range of frequencies – perceptual or otherwise.

    To convincingly state that something which exists only in the realm of human perception has the same degree of reality as something which exists both in human perception and in the physical world, would require a form of argument well outside the realm of color theory, and such has not been provided here.

    Thus I, and hopefully everyone else with a healthy mind, remain unconvinced.

  3. Reggie November 14, 2013 at 1:02 pm - Reply

    It is simply not true that all color is subjective. Were it so, color would lose most of the meaning we ascribe to it.

    I happen to be partly colorblind, and sufficiently so that a great many green traffic lights have an effectively white appearance. This can cause perceptual confusion at night, when I will occasionally not realize that I have “run a green light” until I am already partway through the intersection! While highly disconcerting, this experience fortunately is quite harmless.

    Yet when stopped at similar intersections for a red light, when the light changes from red to something else, I know that it has changed from red to green not due to any experience of greenness on my part, but rather due to other cues – such as the absence of redness or yellowness, and the presence of the new illumination at the top of the the semaphore, and especially the simple fact that is was a transition away from red, and the understanding that the colors happen in a known sequence. In this way, I know that it is a green light with more than sufficient reliability to drive safely.

    If however tomorrow I were to remain parked at the intersection when the light changes from red to something else, due to an absence of any personal perception of greenness, should I give the police officer your name Melissa, and that of SciAm’s Michael Moyer, as published authors who might be willing to argue that a green light is not a green light?

  4. Reggie November 14, 2013 at 1:08 pm - Reply

    Edit:
    c/top/bottom/
    c/is was/it was/

  5. JohnnieZ November 14, 2013 at 3:43 pm - Reply

    To Will: The light blue has a name, “baby blue.” The light greens have names as well, such as, “mint green,” “Lime green,” etc. Just about every shade of the primary colors has a name, or more than one name.

    • Will November 14, 2013 at 4:16 pm - Reply

      JohnnieZ: There is a big difference.

      Baby BLUE, Mint GREEN, Lime GREEN. Each of these has descriptors associated to the root name. Following this logic, everyone should call this color “Pink Red”, not just “Pink”.

      More importantly though, it’s less about the classification of the color than it is about the attitude people have towards it.

      For example, if I were to call something that is mint green just “green”, how many people would challenge me? On the other hand, if I were to call something that is pink “Red”, how many people would feel it necessary to *correct* me? I’d be willing to bet it’s a big difference.

      My point: If pink is just a low-saturation red, why does it get treated like it’s not just a variation of red?

      What makes Pink so special?

  6. Fred Prince November 15, 2013 at 2:29 pm - Reply

    ‘Pink’ derives its name from a kind of flower, which, in turn, derives its name from the ragged edges of its petals. Thus we also have ‘pinking shears’, commonly found in the tools of seamstresses to cut sawtoothed edges on cloth.

  7. Mateo Jose November 17, 2013 at 2:22 pm - Reply

    While we’re on the subject, I was thinking… cold, silence, and darkness… none of them exist. Cold is an absence of heat. Silence is the absence of sound. Darkness is the absence of light. Even though the 3 things don’t exist, we still give them names because we need placeholders. Am I right? Feedback appreciated.

  8. Fursday January 28, 2014 at 12:41 pm - Reply

    Will’s question really fascinates me.

    Does pink have its own name because something in our brain makes this saturated varient of red stand out more than light-green and light-blue?

    Or is the reverse true; are we conditioned by our upbringing to notice it more, simply through being taught it as a distinct catagory from a young age?

    And the same is true of orange. Orange is roughly somewhere between red and yellow – itself a mixture of red and green in the RGB model. To put it another way, orange is yellow with more red in it than green. Something most of us would consider orange could be made by mixing twice as much red light with green light.

    So why not a separate name for the colour that exists between yellow and green? (twice as much green light as red light), or for those colours that exist between cyan and blue or between cyan and green?

    Are we just less sensitive to them or does the lack of linguistic distinction make this the case?

    Interestingly, names of colours occured in cultures in roughly the same order (http://gizmodo.com/how-the-colors-got-their-names-1510522700) – long before we separated pink, purple and orange, even yellow and green were seen as one and blue didn’t exist at all!

    Did these ancient peoples make less of a distinction due to an absence of identifiers or did colours happen in an order because some (like red one of the first) stand out more?

  9. Fred Prince January 28, 2014 at 4:52 pm - Reply

    I have seen several misconceptions posted regarding the color, pink. I’ll try to clear up some of them.

    After Isaac Newton used a prism to separate the colors of sunlight into the visible range, he added another experiment, He placed an opaque sheet with a narrow slit an a second prism in the path of the ‘rainbow’ pattern.

    At any position along the colors the second prism did NOT further separate colors. The colors along the visible spectrum are ‘basic’ or, as they are now called, ‘primary’.

    It is possible to simulate any color you would like by using any three narrow colors. Computer printers use CYMK (K-black for darkening the result). The computer screen uses RGB.

    It is a myth that RYB are ‘the’ primary colors. THey are commonly used in art, because the available pigments ‘behave’. They can be sufficiently pure to produce attractive and useful ‘secondary’ colors.

    Green is a range of energy levels within the color in the visible spectrum. The spectrum represents a continuous range of energy, with red at the lower energy level and violet at the higher end. Orange is primary, in the same sense, as green, indigo and violet. In computers, cyan and magenta are also ‘primary’ colors.

    Due to limitations in our retinal pigments, we only have the ability to see ‘colors’ outside of the visible range. Many animals, including bees and birds, can detect colors that we cannot. Other animals, like dogs and bulls, cannot see as many colors as humans. Bulls attack movement, not red objects.

    Hot solids and compressed gases emit energy in a wide range of energy levels from barely warm (far infrared) to radio, microwaves, X-rays and more.For these objects the spectrum is continuous, without breaks across the energy range.

    Incandescent light bulbs produce a continuous spectrum between far infrared and ‘hotter’ colors.You can buy UV bulbs (black light) that emit ultraviolet light, which is even more energetic than ‘visible’ light.

    ‘Thin’ gases tend to absorb specific energy levels related to their atomic structure. This energy causes a movement of the electrons to higher orbits. When the electrons emit photons, they have the same enrgy levels as the originally absorbed light. However, the emitted light is scattered, causing narrow gaps in the no longer continuous spectrum, Thesew are called ‘Fraunhoffer’ lines, which help to identify the elements in thinner gases between us and the light emitters. We cannot identify elements within stars, only in their atmospheres.

    Light emitters emit light with vatiable energies, The old mnemonic for classifying stars was OBAFGKM (Oh, be a fine girl. Kiss Me.) Type O stars emit bluish light, and type M stars are reddish. Blue has higher energies and red lower energies. The modern classification of astronomical objects has a more complex pattern, with invisble (barely any energy emitted to objects that emit X-rays, etc)

    It is important to understand both the additive and subtractive color processes. Black contains 0 percent energy at all parts of the spectrum. White can be thought of as 100 percent of intensity all through the visible spectrum. ‘Grays’ have a relatively even dispersion of all colors at intensities between 0 and 100 percent.

    Natural pigments tend to reflect an uneven range of colors (maybe like the familiar ‘bell’ curve). The peaks in this distribution determine what colors we see. For instance ‘greens’ may actually reflect a range in colors from all across the spectrum.

    When you see fall colors in leaves, these pigments were probably there all year. The green leaves are a mix of colors, which is very difficult for a painter to reporduce. When we mix orange to green, our typical paints yields a ‘muddy’ color.

    Pink is a very light gray with more red included.

    As I said in an earlier post, we get our name for the ‘pink’ of those flowers. The petals on ‘pinks’ have frilled edges. Trimming fabic during tailoring is often done with special scissors that cut a zig-zap line. This is to reduce the threads pulling apart from the fabric edges, and is done with ‘pinking shears’. Both the color, ‘pink’ and the special scissors were named after the associated flower.

    Surprise an art teacher sometime by mixing powdered tempera paint using the RYB ‘primaries. The resulting colors are produced because each pigment ‘subtracts’ parts of the spectrum. The colors that you might predict do not appear.

    If you mis ‘blue’ and ‘yellow’ pigments, both will reflect green, because they won’t absorb all the green within them. But, try it to see what you really get from mixing paint powders.

    It’s terribly messy, but interesting. Seeing is believing.

  10. Justin Biebef March 18, 2014 at 4:12 pm - Reply

    What!?!?!? No green is not a primary colour!!!! Its Blue, Red and Yellow!!!!!

  11. Rere April 9, 2014 at 6:09 pm - Reply

    This was fascinating! FYI, your link for Minute Physic’s YouTube page doesn’t work. I found it on my own, but just thought you’d like to know. :)

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