Color is a perception created when light interacts with the world and reaches the human eye. Visible light is a form of electromagnetic radiation, where each color corresponds to a specific range of wavelengths. When light hits an object, some wavelengths are absorbed while others are reflected. The reflected light is what our eyes register as color, and all hues are ultimately created from a small, fundamental set of light wavelengths.
Defining the Primary Colors of Light
The primary colors of light are Red, Green, and Blue (RGB). These three wavelengths are primary because they directly correspond to the three types of cone cells in the human retina responsible for color vision. Each cone type is maximally sensitive to light in the short (blue), medium (green), or long (red) wavelength regions of the spectrum. By stimulating these three cone types in varying combinations, the brain constructs the perception of almost every color visible to humans.
The Mechanics of Additive Mixing
The process of combining these light colors is known as additive mixing because each color adds its energy to the total, resulting in a brighter final color. Combining Red and Green light produces Yellow. Combining Red light with Blue light yields Magenta. Mixing Green light with Blue light results in the secondary color Cyan.
These three secondary colors—Yellow, Magenta, and Cyan—are formed by mixing two primaries at equal intensity. When all three primary colors (Red, Green, and Blue) are mixed together in equal proportions, the combination results in the perception of pure white light. Digital devices like computer monitors utilize this model, using tiny red, green, and blue light emitters to generate the millions of colors seen on the display. Stage lighting systems also rely on additive mixing to create custom colors.
Understanding Additive Versus Subtractive Color
The additive color model contrasts with the subtractive color model, which describes how pigments or inks work. The fundamental difference is that light-based colors work by emission, while pigment-based colors work by absorption. In the subtractive model, Cyan, Magenta, and Yellow are considered the primaries. When mixing paints or inks, the pigments absorb, or “subtract,” certain wavelengths of light and reflect only the remaining ones.
Because pigments subtract light, mixing more colors results in a final shade that is progressively darker. When all three subtractive primaries (Cyan, Magenta, and Yellow) are mixed, they absorb nearly all visible light wavelengths. This absorption results in a very dark color, often perceived as black. Conversely, the additive model starts with black (no light) and builds toward white (all light), while the subtractive model starts with white and builds toward black.