Red, Yellow, BlueIt is common for educational materials to claim that red, yellow and blue are only primary colors. It is true that these are all spectral colors that can produce a wide gamut of colors using additive color mixing. However, it is not true that these are the only primary colors or that these have some special properties that other sets of primary colors lack. It should also be noted that primary colors do not produce all colors but instead simulate most colors. For example, violet can be simulated with purple using red and blue but this isn't true violet.
Spectral ColorsSpectral colors are the colors that are produced by pure wavelengths of light in different bands. This includes all visible light. The spectral colors aren't usually viewed as primary colors but they are in the sense that they are required to truly reproduce all colors found in nature. A technology based on spectral color would theoretically produce noticeably more diverse and authentic colors than a technology based on three colors.
|Spectral Color||Wavelength of Light|
Red, Green, Blue (RGB)It is common for display technologies to use red, green, blue (RGB) as primary colors in an additive color model. The exact colors chosen by these models relate to the colors of the phosphors used in the technology. Some colors produced by RGB technologies can be considered simulated such that they differ from the wavelengths of light in natural color.
Cyan, Magenta, Yellow and Key (CMYK)The primary colors cyan, magenta and yellow are commonly used in subtractive color models by technologies such as printers. A fourth color known as "key" is black ink that is used for efficiency that is unnecessary to the color model. In other words, it is inefficient to use a mixture of cyan, magenta and yellow to simulate black so black ink is used instead.
Common MythsThere are several common misconceptions related to primary colors:There is only one set of primary colorsNot true, there are different sets of primary colors associated with different color systems that can be either additive or subtractive.All colors in nature are made of primary colorsNot true, all visible light is found in the colors of nature. Primary colors relate to color systems such as a display technology and not to nature itself. For example, the color violet below is being displayed on your screen right now using the primary colors red, green and blue. This is corresponds to mixed wavelengths of light from the bands 625–740 nm, 500–565 nm and 450–485 nm.
Violet#9a0eeaIn nature, violet is produced by pure light in the range 380–450 nm. As such, what you see above is really purple. As HTML/CSS colors are based on RGB they don't support true violet as can be seen in a flower or sunset.Primary colors produce all other colorsNot true, primary colors simulate most colors but there are noticeable differences from real colors. This is particularly true when primary colors are used to simulate a spectral color such as violet, green or orange. Primary colors also tend to produce an off-black as opposed to a true black. This is so noticeable that most technologies produce black with some special method as opposed to using primary colors. The set of colors produced reliably by a color system using primary colors is known as a color gamut.
NotesMany of the myths perpetuated by educational materials regarding primary color become fact if you are talking about spectral colors. For example, all colors are made up of spectral colors and not primary colors. It is curious that primary colors are taught, when these are arbitrary colors selected by a color system as opposed to spectral colors, that are a foundational aspect of human color perception.
|Overview: Primary Colors|
|Definition||A set of colors from which most other colors can be obtained or simulated.|
Colorimetry »Spectral Colors »Purple »Red »Blue »Violet »