What are primary colors?
A common definition is that primary colors are the colors that can be used to make all other colors, and that the primary colors cannot be made by mixing any colors. Most elementary school instructors teach that red, yellow, and blue are the primary colors. All parts of this definition are either wrong or inadequate.
First: there is no one set of colors that can produce all other colors. Almost any three or more colors can be mixed to produce all the other hues. (The three colors can't all be on the same half of the color wheel at the right.) But there is no set of primaries that can produce all the hues in all their values and in all their chromas. (See the Hue, Value, Chroma page.)
Second: all colors, even primary colors, can be produced by mixing other colors. But no color can be produced at its maximum level of purity by mixture of other colors.
Third: red, yellow and blue are never the best primary set. They can produce all the hues, but they produce magentas and purples very poorly, and they don't produce very pure greens.
And one more thing: we need primary colors with different characteristics, depending on whether we are mixing colors additively, or subtractively—What?!?!
|Additive Color Mixture
|Subtractive Color Mixture
|Additive color mixture begins with the absence of light (black), and adds colors of light together to form new colors. Additive mixture is used in theatrical lighting, and in computer monitors and TV screens.Red, green and blue are typically used as the additive primary colors. (Examine your computer screen or TV with a very strong magnifying lens, and you'll see that the image is made up of a matrix of red, green, and blue pixels.)
||Subtractive color mixture begins with the presence of all colors (white), and subtracts, or absorbs, colors of light from the white light to form new colors. Subtractive mixture is used everywhere. Virtually all painting, printing, dying, and photography use it. Cyan, magenta and yellow are often used as the subtractive primary colors.
Follow these links to learn more about additive and subtractive color mixture.
Click here to play in the Color Sandbox, with additive color mixture.