Color

Color is a visual property that arises from how light reaches the eye and how the brain interprets it. Visible light is part of the electromagnetic spectrum with wavelengths between approximately 380 and 750 nanometers. Shorter wavelengths are perceived as blue or violet, and longer wavelengths as red.

Color is not solely a property of an object. It results from three interacting factors: the light falling on the object, how the object absorbs or reflects the wavelengths, and how the visual system of the observer processes this information. For this reason, the same object can appear a different color when the light source changes.

Color vision in the eye

The human eye contains light-sensitive cells in the retina. Cells called rods work in dim light and distinguish light from darkness. Cone cells distinguish color; people with typical vision have three types of cones, each sensitive to short, medium, and long wavelengths. This three-channel system is called trichromacy and is the basis for the three primary colors on screens.

Color mixing

There are two forms of color mixing. Additive mixing works by combining light: red, green, and blue light mixed together produce white light, and this is how television and computer screens work. Subtractive mixing works with pigments and inks, where the primary colors are cyan, magenta, and yellow, which absorb part of the light.

Color properties

Each color can be defined by three properties: hue (type of color, such as red or green), saturation (intensity or purity), and brightness or lightness. Color systems such as RGB, HSL, and CIE use these properties to measure and transfer colors between devices.

Color blindness and variation

Some people have atypical color vision, often linked to variation in cone cells. The most common form is difficulty distinguishing red and green. Language also affects how colors are perceived: the way colors are named varies across languages, even though the physical wavelengths are the same.