primary colour

 

Three Primary Colors (Ps): Red, Yellow, Blue. Three Secondary Colors (S'): Orange, Green, Violet.

 

Biological basis[change | change source]

Primary colors are not a fundamental property of light but are related to the physiological response of the eye to light (the way the eye works). For humans, three primary colors are usually used, since human color vision is trichromatic.

Fundamentally, light is a continuous spectrum of the wavelengths that can be detected by the human eye, an infinite-dimensional stimulus space.^[3] However, the human eye normally contains only three types of color receptors, called cone cells. Each color receptor respond to different ranges of the color spectrum. Humans and other species with three such types of color receptors are known as trichromats.^[3]

The additive primaries are red, green, and blue. Because of the response curves of the three different color receptors in the human eye, these colors are optimal in the sense that the largest range of colors — a gamut — visible by humans can be generated by mixing light of these colours. Additive mixing of red and green light, produce shades of yellow or orange. Mixing green and blue produces shades of cyan, and mixing red and blue produces shades of purple and magenta. Mixing equal proportions of the additive primaries results in shades of grey; when all three colors are fully saturated, the result is white. The color space that is generated is called the RGB ("red, green, blue") color space.