The result of mixing all colors depends entirely on the medium being combined. The final color is determined by whether you are mixing physical substances, like paints or inks, or if you are combining sources of light. The underlying physics of how we perceive color changes completely between these two scenarios, leading to opposite outcomes.
Mixing Physical Colors (The Subtractive Model)
Mixing physical substances, such as paint, inks, or dyes, operates under the principle of subtractive color mixing. This model is named “subtractive” because each pigment added to the mixture absorbs more wavelengths of light from the visible spectrum. The primary colors in the subtractive model are Cyan, Magenta, and Yellow (CMY), which form the basis for all modern color printing.
When white light strikes a colored pigment, the pigment absorbs all wavelengths except the one it reflects back to the eye. For instance, cyan ink absorbs red light, magenta absorbs green light, and yellow absorbs blue light. Mixing two of these primaries causes them to collectively absorb two of the three additive primaries, leaving only one color to be reflected.
The final mixture of all three primary subtractive colors—cyan, magenta, and yellow—absorbs virtually all visible light. The resulting color is black, or in practice, a very dark, muddy brown or gray due to pigment impurities. Subtractive mixing is therefore a process where adding more color makes the result darker, moving from white (the paper) toward black (the total absorption of light).
Mixing Light (The Additive Model)
In contrast to physical materials, combining colored light sources follows the additive color model. This model is called “additive” because the energy from the different light wavelengths is combined. This process is the foundation for all digital displays, including television screens, computer monitors, and stadium lighting.
The primary colors of light in the additive model are Red, Green, and Blue (RGB). When two of these light primaries are combined, they create the subtractive primaries: Red and Green light create Yellow, Green and Blue light create Cyan, and Red and Blue light create Magenta.
When all three additive primaries—Red, Green, and Blue—are projected onto a surface and fully overlap, they stimulate all three types of cone cells in the human retina equally. This full, balanced stimulation across the short, medium, and long wavelengths is perceived by the brain as white light. This means that combining all colors of light results in white, the brightest possible outcome, because all light energy is present.
The Science Behind the Different Outcomes
Colored light actively emits energy, while pigments merely filter or absorb the light that is already present. Light mixing is a process of superposition, where the energy of the red, green, and blue light waves sums up to create a full spectrum, which is white.
Pigments do not emit light; they selectively reflect portions of an external light source. A yellow pigment appears yellow because it absorbs the blue portion of the white light and reflects the red and green portions. When multiple pigments are mixed, each one continues to absorb the wavelengths it did before, leaving fewer and fewer wavelengths to be reflected.
The relationship between the two systems is complementary: the three subtractive primary colors (CMY) are the secondary colors created by mixing the three additive primary colors (RGB). This is because each subtractive primary color is simply white light with one of the additive primaries removed. For example, Cyan is white light minus Red light, which leaves Green and Blue light combined. Therefore, combining all pigments completely filters the entire light spectrum, resulting in the absence of reflected light, which is perceived as black.