Primary colors: what they are, and characteristics

Color is a visual experience. That is, it is a sensory impression that occurs thanks to the fact that we have three types of color receptors in the retina: the cones. These receptors respond to very specific wavelengths.

Although most of us see thousands of different colors, really most of these are combinations of three essential colors: the primary colors. Next we are going to see what they are exactly, what color theories exist and the concept of the chromatic circle.

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What are the primary colors?

The primary colors are those that cannot be obtained by mixing with other colors, reason for which they are considered unique and singular. However, it is possible to mix them together, obtaining a wide range of tones with them.

Although the idea that the three primary colors are red, yellow and blue is well established in popular culture, in reality, these three are not the true pure primary colors. exist different chromatic models that, depending on whether the color is due to a material or light, the primary colors are one or the other

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What most chromatic models do have in common is that they defend the idea that there are always three primary colors, although they differ from model to model. This is because the human eye has trichromatic vision. This peculiarity is due to the fact that in the retina we have, most of us, three types of receptors that respond to very specific wavelengths of light: the cones.

Theories of primary colors

There are different theories about primary colors, two of which are the most influential: that of light colors, or additive theory, and that of pigment colors, or subtractive theory.

additive theory

Light color is immaterial, created by sunlight or artificial light. Light colors are obtained from the sum of radiation of different wavelengths and in different proportions..

The primary colors within the additive system are red, green and blue, constituting the RGB model (Red, Green and Blue). These colors are in white light, and are obtainable if that same light is decomposed with a prism. In turn, combining red, green and blue light we obtain a beam of white light.

The primary colors of the additive system can be combined in pairs, giving the following secondary colors:

Red + green = yellow.
Red + blue = magenta.
Green + blue = cyan.

In addition, the absence of primary tones causes the color black to emerge. This is because the human eye is not able to recognize the tones in the environment if there is no light in the environment.

Because you can play with the lights to obtain different colors, this is the system used by devices that work through light emissions, that is, screens.

subtractive theory

Subtractive primary colors are those found in pigments and dyes., being magenta, yellow and cyan, called the CYM model (Cyan, Yellow and Magenta).

Formerly, it was believed that color was a quality of the object. However, with advances in optics and it was discovered that the color we see in an object is due to what type of light is reflected on it.

Depending on the pigment that the object has, the white light that falls on it is incompletely reflected. On the one hand, some light beams will be absorbed by the same object, while others will be reflected. The reflection is what the human eye captures, assigning it the color from which we see the object.

For example, let's imagine a magenta-colored object. As we have already said, white light has all the colors in it. This light, when hitting the object, is partially absorbed, absorbing all the colors of the visible spectrum except magenta, which bounces and is what we end up seeing.

As with light colors, subtractive primary colors can be combined to form secondary colors.

Magenta + yellow = red.
Yellow + cyan = green.
Cyan + magenta = blue.

Curiously, from the combination of the subtractive primary colors we obtain, as secondary colors, the colors that are primary in the additive model. Conversely, by combining the additive primary colors we obtain, as their secondaries, the subtractive primary colors.

Unlike light colors, which combined result in a white light beam, pigment colors mixed together result in black.

Since these colors are directly related to the pigments of an object, the system of subtractive primary colors is used in pictorial or printed elements, such as pictures, banners, books, colors of industrial objects.

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traditional primary colors

Originally primary pigment colors were thought to be the same as we have today in popular culture: yellow, red and blue.

In fact, the famous German philosopher Johann Wolfgang von Goethe defended this idea in his 1810 book Zur Farbenlehre (“Color Theory”). In that book he created a model that we could call RYB if it had triumphed (Red, Yellow and Blue), being represented in a chromatic circle and where they joined to form other, secondary colors. This model would be the precursor of the current CYM model.

Although this system has become obsolete, it is still used in plastic arts, especially in courses focused on primary school children.

The psychological primary colors

The theory of psychological primary colors was exposed by Ewald Hering. In her included up to six primary psychological colors, grouped in opposite pairs, namely: black and white, red and green, yellow and blue.

Although in plastic arts this theory has not had much impact, it has had it in the study of visual perception, being demonstrable in practice. For example, if you stare at a green object and then look away to a surface white or black, the silhouette of the object remains fixed on the retina, but seeing its opposite color, which would be the red. This same process can be repeated with objects of different colors, appearing, in effect, its opposite color.

Origin of the color wheel

Isaac Newton was one of the first to study primary colors and their derivatives, expounding his theory in his book Opticks: or, A Treatise of the Reflexions, Refractions, Inflexions and Colors of Light (1704). In it he affirmed that there were seven basic colors in light, which were those that can be seen in the rainbow: red, orange, yellow, green, turquoise, blue and violet. In addition to this description, he made great contributions to optics with the creation of the first color wheel.

The color wheel, as we know it today, arises from the primary colors. In this circle the primary colors are located in equidistant positions, where the mixture of two of them will give rise to the secondary colors. From the mixture of a primary color with its secondary a tertiary color arises.

Newton is credited with the discovery that the colors we perceive can be identified thanks to light, as we have explained before in the subtractive theory section. When light falls on an object with a certain pigment, it breaks down, bouncing the non-absorbed light and absorbing the rest. It is that unabsorbed light that gives color to the object in question.

Bibliographic references:

Newton, Isaac (1998). Opticks: or, a treatise of the reflections, refractions, inflexions and colors of light. Also two treatises of the species and magnitude of curvilinear figures. Commentary by Nicholas Humez (Eighth ed.). Palo Alto, Calif.: Eighth. ISBN 1-891788-04-3.
Goethe's Theory of Colours: Translated from the German; with Notes by Charles Lock Eastlake, R.A., F.R.S. London: John Murray. 1840.