Biology 103
2002 Second Paper
On Serendip

Color is a difficult quality to explain because it is the one characteristic that can mark the difference between two objects exactly the same all other physical traits, such as size, shape, and texture (2). Putting words to the difference between an item that is red and one that is yellow is harder than describing the difference between an item that is tall and one that is small. It is almost impossible to avoid purely subjective and emotional words when describing color. Also, we only know how to assign a. specific word to a color because we are trained to. How else can we know how to give red the word "red" if a kindergarten teacher never holds up those color flashcards? Therefore, in order to understand what color really is, it is necessary to understand how it is produced.

Colors can be defined by two different processes. The first is the physical diffraction of white light and the other is the interaction between electrons within a molecule and light. White light is a mixture of many colors and when it hits, for example, a prism, it splits into different components in a flat spectrum. Each component of the light has its own wavelength, thus yielding what we perceive as color (1).

A chemistry-based approach of defining color deals with the energy of an electron inside of a molecule. An electron can be excited from a lower orbital to a higher orbital by absorbing a specific wavelength of light and "the loss of this wavelength from the balanced white light source results in color (1)." Seeing pigment color is a process dependent on the actual molecules of the object, how those molecules interact with light, and how our eyes perceive that interaction. This can be explained by the concept of turning out the lights on a red chair- did the red chair become any less red? The answer is "yes"- even though turning off the lights does not change the molecular structure of the chair, red can only exist because of the light. The electrons in the molecules of the chair can only interact with the light. The chair is not red because the molecules create red. The molecules in the chair's pigment absorb all other wavelengths and reflect certain wavelengths back (1). Furthermore, this process only matters when our eyes process the light. This is the step in which our visual system captures those wavelengths, processes them through our retinas, interprets them in our brains, thus allowing us to give one word for that whole experience, "red." However, both processes send the same wavelengths, so the eyes and brain know that red means red, no matter if we see it in a rainbow or in the pigment of the chair (1). The eyes and brain can do this because of the nature of our biological visual system.

The biological process that enables us to see color is a subjective experience. It begins with "the stimulation of the light receptors in the eyes," leading to the conversion of light stimuli or images into signals, and then the, "transmission of electrical signals containing vision information to the brain through the optic nerves (5)." We are capable of seeing color due to the photoreceptors in the retina of the eye that are sensitive to light. There are two kinds of photoreceptors in the retina- rods and cones. Rods are receptive to amounts of light while cones are sensitive to different colors (2). There are three types of cones and each type is sensitive to the different-sized wavelengths of the visible spectrum. Long wavelength or "red" (R) cones, which are most sensitive to "greenish yellow" wavelengths, middle wavelength or "green" (G) cones, most sensitive to "green" wavelengths, and short wavelength or "blue" (B) cones, most sensitive to "blue violet" wavelengths (6). From this information arises the "trichromatic color theory", that says the primary colors are red, blue, and green (6). Basic neural programming transforms the basic outputs of these three cones into four channels of chromatic color signals and a colorless channel that determines brightness. Therefore, our perception of color comes from the amount and type of light being absorbed by each cone type (2). Also, our color vision follows some basic rulesthe stimulation of the R and G cones gives the perception of red and green, when these two cones are stimulated about equally, we perceive yellow, and that the stimulation of B cones creates the perception of blue (6). What makes this process subjective is the fact that the molecules that make up my eyes and brain are not the same molecules that make everyone else's. Therefore, no two people can perceive color the same way. However, even though color is a subjective experience, the idea of complementary colors can exist. Newton made the first arguments for this.

Newton formed a color wheel and, although this may not sound like much, it was revolutionary. His experiments and writings deal greatly with arguing against Aristotelian theory because he wanted to make clear that hue could be conceived and described separately from light and dark (4). To systemize this idea into a process, he had to use the spectrum as a reproducible color reference to identify and name the hues in nature. However, Newton had to overcome the idea of colors existing in just a flat spectrum, only considered to be near or far from one another with. By thinking in terms of a circle, Newton automatically discovered that colors can be linked together and have relationships. However, he did not just bend the spectrum into a circle to form relationships between colors. He specified the rules for color's placement on the wheel with geometry and physics. He determined that, "saturated hues are on the circumference of the circle, white or gray is at the center, complementary colors are opposite each other on the circle, and the color of a mixture is located at the 'center of gravity' of all of the hues in the mixture weighted by their brightness (3)." Through these ideas, Newton gave words that eradicated the subjectivity in the process of linking colors together. He gave a color's placement on the wheel physical justification. However, Newton relied on the principles of light to make predictions about how both types of color mix. This was misleading because he did not take into account that pigment color does not work the same way as light coloration (3).

I am arguing, though, that there really is a connection between pigment colors in the form of a color wheel too. Yes, yes- pigment color cannot be clearly defined because seeing it really is a subjective process dependent on ever-changing light and on our different biological systems. However, these concepts do not erase the scientific reasons that uphold the existence of complimentary pigment colors.

Ewald Hering argued for the existence of non-arbitrary but scientific relationships between pigment colors when he proposed his own color wheel that was based entirely off of the subjective experience of color (6). Although he understood the trichromatic color theory, Hering was not satisfied with it. This color theory cannot explain why yellow is psychologically just as primary as red or blue or green; nor can it explain either why we can visualize mixing red with yellow to get orange but not red with green and to get red-green (6). He devised a color wheel of his own to answer his questions. By saying that red, blue, yellow, and green are the four fundamental hues that can be contrasted to one another, blue to yellow and red to green, Hering made the connection between the subjectivity of our perception and the existence of complementary color for pigment. He justified their relationship as opposites through the fact that they can be mixed to form any color that appears on the spectrum (6). It turns out that these complements, and not the raw R, G and B cone responses, are the better framework for describing the discrimination between two very similar colors and the prediction of hues in a color mixture. This is because the "translation from receptor responses to opponent codings happens in the retina: the brain never "sees" the trichromatic outputs (6)." So the four colors of red, blue, yellow, and green, and not the three "primary" colors of the color receptors, led to developing a color model that respects how color is more than just our different perceptions. This allows for the existence of judgments that can be made consistently over time by more than just one person and for color theory. Hering had devised a color system that can understand our biologically subjective experience and look beyond it to describe what else is also going on in the relationships between colors.

Hering's color wheel just began to tap into the connections between pigment colors that do exist for mathematical and scientific reasons. Furthermore, his is not the only color wheel but to explain all of them and to trace their evolution requires far more space than I have here. However, Hering's color wheel alone gives me enough support to justify my opinions of my professor's wardrobe. Argue as he might that color is purely subjective because it is really an experience dependent upon light and molecules, how colors connect is not subjective. Colors have relationships that are upheld by science. The new questions that come up ask how more does the brain and psychology play a part in determining color relationships, why we tend to associate feelings with color, and how much is more advanced color theory subjective..

References

1) Dr. K.D. Luckas. Chemistry 104 Laboratory Manual: Supplement for the Major's Section. Bryn Mawr College; 2001.
2)RIT Munsell Laboratory, FAQ section on the RIT Munsell Color Science Laboratory website
3) page that discusses "Mixing with a Color Wheel" , the color section on this website a good source for information about all aspects of color
4)"Color Psychology", page that discusses "Color Psychology"
5) Molecular Expressions website , page that discusses light and color
6) Opponent Processing of Color, page that discusses "Light and the Eye"


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