The question of which colors create yellow has two completely different answers, depending on the physical medium involved. Color mixing is governed by two distinct systems: the additive model, which applies to light sources, and the subtractive model, which applies to physical materials like paint and ink. The principles of physics and human perception dictate that yellow’s composition changes entirely based on whether you are adding light or absorbing it.
Creating Yellow Through Light (Additive Color Mixing)
In the world of light, color is created through the additive system, where combining different wavelengths results in a brighter color. The primary colors of light are Red, Green, and Blue, often referred to as the RGB model used in digital displays. When light from two of these primary sources overlaps, a new, secondary color is produced.
To create yellow light, you must mix Red light and Green light in equal measure. This process is used in all modern electronic displays, such as computer monitors, televisions, and smartphone screens. When the red and green light-emitting components within a pixel are illuminated simultaneously, the resulting combined light is perceived as yellow.
This result occurs because of how the human eye processes light using three types of cone cells. These cones are sensitive to short (blue), medium (green), and long (red) wavelengths of light. When pure red light and pure green light hit the eye at the same time, the brain receives a combined signal. This simultaneous stimulation is interpreted by the visual cortex as the color yellow.
Yellow in Pigment Systems (Subtractive Color Mixing)
For physical materials like paint, ink, and dyes, color mixing operates under the subtractive system, which involves the absorption of light. In this model, the more colors you mix, the darker the resulting hue becomes because more wavelengths of light are being filtered out. For commercial printing and professional applications, the standard subtractive primaries are Cyan, Magenta, and Yellow (CMY).
In the CMY model, yellow is a fundamental primary color, meaning it cannot be created by mixing any other two pigments. A pure yellow pigment works by absorbing blue light while reflecting both red and green light back to the observer’s eye. If yellow were mixed from other pigments, the resulting color would be significantly darker and duller.
The traditional Red, Yellow, Blue (RYB) color model, familiar from early art education, also defines yellow as a primary color. Attempting to mix two non-yellow pigments, such as red and green paint, will not yield yellow. Instead, the combination of two pigments absorbing various parts of the spectrum results in a muddy, brownish, or dark neutral color. This requires yellow to be a starting component for creating other colors.
The Scientific Definition of Yellow
Moving beyond mixing techniques, yellow is defined by its physical properties within the electromagnetic spectrum. Yellow light occupies a specific, narrow band of wavelengths that the human eye is capable of detecting. This spectral region typically falls between approximately 570 and 590 nanometers (nm).
Light existing at this precise wavelength is referred to as “pure” or spectral yellow. When this specific wavelength enters the eye, it directly stimulates the long- and medium-wavelength sensitive cone cells. While the perception of yellow can be achieved by mixing red and green light, the existence of spectral yellow confirms its identity as an objective point on the visible light continuum.