To understand which colors in the color spectrum fall into a category called subtractive colors and how this type of color mixing works, we must first break down how light works to translate color to the human eye and allow us to see objects in different hues.
Once we work through that process, we will look at subtractive colors that, when combined, subtract types of light waves until none reflect from the given object, as well as additive colors that, once mixed, add in more types of light waves until all reflect together.
How We See Colors
In order to make any type of vision possible, the parts of the eye are structured to refract light that enters the eye and receive and translate it into information that gets passed to the optic nerve, which then transfers it to the brain as visual information. When light, which travels in wavelengths, reflects off of an object and enters the eye, the outer layer called the cornea refracts, or bends, the light to pass through the lens to the retina. This process allows the light energy to be read by rod and cone cells in the retina, each of which are designed to receive different points of information like identifying a particular color.
Light is made up of energy which occurs in wavelengths, and the frequency, or size of the wave, determines the color. White light contains energy from all colors—red, orange, yellow, green, blue, indigo, and violet—mixed together, while black results from the absence of colored light energy. Pigments, the substances in an object that absorb color, have certain characteristics that determine which size wavelengths they can absorb and which they will reflect. When an object appears blue to us, this happens because its pigmentation has absorbed the wavelengths of red, orange, yellow, green, indigo, and violet light and is reflecting the blue light. This light energy then enters our eye and travels back to the retina, where rod and cone cells translate that information and relay it to the optic nerve and then the thalamus in the brain where it registers in our mind as sight. This is how humans see color.
Real-World Colors and Media Colors
With the process of how our eyes send information to the brain and the way in which pigments influence which colors we detect from an object in mind, we can conceptualize an illustration of how different colors are subtracted, or absorbed, from the mixture of light until we are left with one color that is not absorbed but reflected. This is the color that we visually see. However, this is merely a demonstration of that idea.
When dealing with actual physical objects in the three-dimensional world, the particular color of an object we see is actually the color that results from the one type of light waves not absorbed by the object’s color pigments. If you observe a yellow sports car, pigments in its yellow paint are absorbing light waves of red, orange, green, blue, indigo, and violet, and reflecting the yellow light waves, making us see the car in that color. To create any product in a particular color, pigments are used in the formula to control which type of light is reflected. Visualize pigments as a series of filters, absorbing all the other shades by sorting them in wavelength sizes and deciding what to let through. Depending on which of the multitude of different shades or color combinations is desired, we can imagine how these filters get very specific and unique.
The idea of subtractive colors is actually a concept within scientific color theory, and it works to achieve various colors and shades by starting with white, which in terms of light is a mixture of all colors, and ruling out all colors that aren’t required in the recipe of the desired color. On the other end of the spectrum, if all colors were subtracted via pigments, we would be left with black as the color our eyes would see.
That describes the way we see and create color in the physical world, but in modalities that use screens, including all computerized devices and even cameras, it works differently. We see words, pictures, and anything else on a screen because of pixels, or tiny sections of a screen that make up the entire picture. When shopping for a new television or other device, you try to find the highest pixel count for the given space that still falls within your price range because more pixels give a clear, crisp image. The default color setting of a screen is black, which you might think of as the screen before you turn on the device’s power, which will turn on its light. We know that black is the absence of visible light, so to achieve color on our screen, light is added instead of subtracted.
Electric charge added to your electronic device brings in colored light in different wavelengths, making the screen brighter and making you see it in color. For each pixel, the fibers respond to the combination of colors to produce the desired shade, receiving the light to reflect the color. A screen made up of each of these tiny points of light is how you view a picture or document on any of your computerized devices. In a reversal of the way pigments allow us to see color in real, tangible objects all around us, if we start with a black screen in digital media and keep adding in light energy in wavelengths of all additive colors, we will end up with a white screen.
We recall that in the subtractive color model, we use pigments to control which colors of light are absorbed, and the one(s) left are reflected, which is the color we see. Starting with white, a combination of all colors of light, we subtract the colors not necessary to achieve the desired color.
The primary colors categorized as subtractive are cyan, magenta, yellow, and black. Black is grouped within the subtractive colors because in working with real tints like paint, printer ink, or even cake frosting, true black proves challenging to achieve. Creators who work with media like this often end up with a clouded dark brown, so pure black pigment is typically used. If we use a printer—or paint—and cover one spot with ink in colors of cyan, yellow, and magenta in equal amounts, together they will absorb all the shades of colored light and we will be looking at a black (or dark muddy brown) spot on the paper.
If we think about the rainbow of colors we learned as children, we recall that red, yellow, and blue (RYB) stand as the primary colors. Mixing red and yellow gets us orange, mixing yellow and blue results in green, and mixing blue with red gives us purple. In print media, red, green, and blue represent the main colors which we can play with and combine to produce a variety of shades. The color cyan partners with red in an inverse way, which is to say, in print media the amount of cyan ink programmed for any spot on a page directly controls how much red should be filtered out of the light and how much should shine through and be visible. Magenta complements the color green, and the percentage of magenta ink in a given spot on a page controls how much green is allowed to be visible there. Finally, yellow serves as the partner of blue, and adding yellow to a combination of ink colors in a spot on a page will control the amount of blue in the shade we see. Keeping printer cartridges full of these colors of ink produces a wide variety of shades from the entire rainbow when each is applied and combined in the right percentage for that color.
Coloring processes that utilize subtractive color mixing are also called CMYK color models, where C stands for cyan, M for magenta, and Y for yellow. The K stands for Key, which represents black ink to further crystallize the graphic when black is desired, and an imperfect delivery of colors from paint or ink results in some version of murky dark brown. The previously mentioned RYB also uses subtractive color mixing, so red, yellow, and blue are also considered subtractive colors when working with this color model.
The primary colors categorized as additive include red, green, and blue. We have learned that if we start with black and add more and more light in colored wavelengths of red, green, and blue, we produce many different shades of the rainbow for viewing. Adding equal amounts of red, green, and blue light together in digital media gives us white. Subtractive color theory tells us that cyan filters red light but lets green and blue shine through, and inversely, on a computerized screen, if we combine green and blue light, it will produce cyan’s brilliant aqua color. Magenta filters out green light, but on a screen, adding red and blue light will produce the jeweled pink-maroon shade of magenta. Yellow controls the amount of blue light but allows red and green through, and in digital media we can combine red and green light to get yellow.
Additive colors and the use of this color model are also referred to as the RGB model in color theory.
Understanding how light works in our vision and how we view certain things in certain shades of color has paved the way for creative efforts in all sorts of media and has served as an important part of art, computer graphics, advertising, and other fields. Now that you have been introduced to additive and subtractive colors, you may be interested in learning more about the difference between additive and subtractive color mixing.