The question of what color red, green, and blue make is not a simple one, as the answer changes completely depending on the material being combined. The outcome is determined by the physical medium, whether it involves beams of light or physical substances like paint or ink. This duality explains why what works on a computer screen is the opposite of what happens on a canvas.
The Difference Between Light and Pigment
Color mixing is governed by two fundamental systems: one based on light and the other on physical material. The system involving colored light is known as additive color mixing, where wavelengths are added together to create brighter colors. The primary colors for this light-based system are Red, Green, and Blue (RGB).
The second system, which applies to materials like paints, dyes, and inks, is called subtractive color mixing. This process works by absorbing, or subtracting, certain wavelengths of light from the visible spectrum. The primary colors for the ideal subtractive system are Cyan, Magenta, and Yellow (CMY).
Combining Red, Green, and Blue Light
When discussing light, red, green, and blue are the foundational colors from which all others are created. This is because the photoreceptor cells in the human eye are most sensitive to these three specific wavelengths of light. The process is additive, meaning that the colors of light are layered on top of each other, increasing the total amount of light energy being perceived.
Mixing any two of these primary lights produces a secondary color that is brighter than the originals. For example, combining Red light and Green light results in Yellow light, while Green light mixed with Blue light creates Cyan. Red light combined with Blue light creates Magenta.
When all three additive primaries—Red, Green, and Blue light—are combined in equal proportions and at full intensity, the result is white light.
Combining Red, Green, and Blue Pigments
The outcome is fundamentally reversed when mixing physical pigments like paints or inks, which operate under the subtractive color model. Since pigments create color by absorbing specific wavelengths of light and reflecting the rest, combining more pigments means more light is absorbed, resulting in a darker color. When Red, Green, and Blue pigments are mixed, the result is typically a dark, murky color, often perceived as a dark brown or a shade very close to black.
The reason for this dark outcome is that RGB pigments are not the ideal primaries for the subtractive system. Although they are sometimes taught as primaries in art classes, their spectral properties are impure. When these less-than-ideal pigments are blended, each one absorbs a large portion of the visible light spectrum.
The red pigment absorbs much of the green and blue light, the green absorbs much of the red and blue light, and the blue absorbs much of the red and green light. The cumulative effect of these overlapping absorptions means very little light is left to reflect back to the viewer’s eye. The true subtractive primaries of Cyan, Magenta, and Yellow are more efficient at subtracting light to produce a cleaner black when mixed.
Everyday Examples of Color Systems
The two distinct color systems are present in many aspects of modern life, determining how color is produced in different media. The additive Red, Green, Blue (RGB) system is used in any technology that emits light to create images. This includes the individual pixels on television screens, computer monitors, and smartphone displays, which illuminate in varying intensities of red, green, and blue to generate millions of colors.
Conversely, the subtractive Cyan, Magenta, Yellow, and Black (CMYK) system is the standard for physical reproduction. This model is used in all forms of commercial printing, such as magazines, newspapers, and desktop printers, which apply layers of ink to a white surface. The subtractive principle is also at work in traditional painting, where artists combine physical pigments to reflect a smaller portion of the light hitting the canvas.