Color Theory – Concept, properties of color, RGB and CMYK

We explain what is the Theory of color, historical examples and the properties of color. Also, RGB and CMYK color models.

Theory of color
The rules of Color Theory allow to achieve the desired effects.

What is Color Theory?

It is known as Color Theory to a set of basic rules governing color mixing to achieve desired effects, by combining colors or pigments. It is a principle of great importance in graphic design, painting, photography, printing and television, among other visual areas.

There is no single theory of colorHowever, but a set of approaches to color and its dynamics. Many of them are part of the history of art or physics (optics), and have different authors.

For example, the pre-Romantic German poet and scientist Johann Wolfgang von Goethe (1749-1832) in his book Color theory By 1810 he already proposed a color circle, based on Isaac Newton’s own studies of matter. Another well-known case is that of Wilhelm Ostwald (1853-1932), a German chemist and philosopher.

One of the main inputs of all Color Theory is the chromatic circle. It is a circular representation of all the colors in the visual spectrum, arranged in such a way that opposing colors face each other and complementary colors are close to each other.

The chromatic circle allows to identify the primary or pure colors, and those that are considered derivatives, that is, the result of the mixture of colors.

According to this type of color studies, each one can be attributed different properties, such as:

  • Hue. Also called “chroma”, it refers to the color itself, which allows us to distinguish one color from another.
  • Brightness. Also called “value”, it refers to the amount of light present in the color, that is, if it is lighter or darker, which is equivalent to saying if it is closer to black or white.
  • Saturation. Basically it refers to the purity of the color, that is, the concentration of gray present in a color at a certain time. The more gray it has, the less pure it will be and the lower its saturation, looking as if it is dirty, opaque.

RGB color model

rgb cmyk color theory
The RGB model is additive while the CMYK model is subtractive.

The RGB color model is so named because of its primary colors: red, green and blue (Net, Green, Blue, in English), from which the rest is composed. It is an additive color system, in which the colors must be added together to produce a new one.

The exceptions are black, which occurs in the absence of light (and therefore color) and white, which occurs in the presence of all colors, recomposing the spectrum. This system is used in most televisions, computer monitors, video projectors, etc.

The CMYK color model

The CMYK model is different from the previous one, but its name is also the union of the initials of the colors taken as reference: cyan, magenta, yellow (in English: yellow), with the addition of black (called Key in English to avoid confusion with the B of the blue RGB).

This model understands color from the absorption of light, so that unlike RGB, it is subtractive, from light subtraction: the mixture of all the pure colors (blue, red, yellow) gives black, the total absence of light.

Furthermore, the various secondary colors can be formed from this matrix, varying the possible combinations of the three: cyan and magenta build purple, cyan and yellow build green, yellow and magenta build red.

This color model is used in various ink printing techniques, since the paper lacks the light properties of monitors or projectors. For this reason, when working in a digital design program, RGB must be converted to CMYK when preparing the design for printing.