This original animation from KET demonstrates how primary colors are sets of colors that can be combined to make a useful range of colors. The two basic ways to produce colors are: (1) using the primary colors of pigments (magenta, cyan, and yellow) to absorb or subtract wavelengths of light, as in mixing dyes, or in printing; or (2) adding various strengths of the primary colors of light (red, green, and blue), as in computer screen pixels.
How do we see color? The answer has to do with the way our eyes react to light and the way our brains decode that reaction. Light is composed of electromagnetic waves, some of which are not visible to the human eye. The waves we see make up what is known as the visible light spectrum. The primary colors in this spectrum are red, green, and blue, often referred to as the primary colors of light. These differ from the primary colors of pigments magenta, cyan, and yellow, commonly called red, yellow, and blue. This is due to the way in which pigments respond to light.
The reason a pigment displays a certain color is the result of how it absorbs some colors and reflects others. In ordinary daylight or artificial “white” light, we see red objects as red because the red light in the spectrum is reflected back at us while the rest of the colors are absorbed and not visible. This process can be visualized using the subtractive color model because the colors that are absorbed are subtracted from the colors in the incoming light, in this case, everything but red. This is the way it works for any pigment color you see. If you mixed another color in with your red pigment, say yellow, all the colors absorbed by the red will still be absorbed and the yellow will absorb still more colors. What you will see is orange, which is how we perceive the reflected colors that neither the red pigment nor the yellow pigment has absorbed.
Television screens and computer monitors both use the primary colors of light, not pigments, to display color. Each screen is made up of thousands of elements called "pixels" that contain components that emit red, blue, and green light. Each of these color components can be adjusted in intensity using a scale of "0" to "1." A "0" value means the color is turned off and not visible. A value of "1" means the color is displayed at its full intensity.
By varying the intensity of each of the three-color components within a pixel, different colors are created. Using just these three colors in different intensities, a single pixel can produce over sixteen million different hues. To create an image on a screen or monitor takes thousands of pixels, each with its own color mixture, working together.
The colors we see on television or computer screens are produced using the additive color model rather than the subtractive color model. That is, these colors result from the light being emitted by the object, not from the object's interaction with sunlight or some other external light source.
To learn more about light and reflection, check out Light and the Law of Reflection.
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