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Why do red and green light beams create yellow when they overlap?

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A circular RYB color wheel divided into twelve segments, showing a progression of colors from red, orange, and yellow to green, blue, and violet. — colour The RYB color model is being illustrated on a color wheel.

Red and green light beams create yellow when they overlap because of the additive color system, a process in which different wavelengths of light are combined to produce new colors.12

Unlike the mixing of pigments—which is a subtractive process that absorbs light—the mixing of light beams is additive. When beams of red and green light are projected onto a surface, they are added together, stimulating the photoreceptors in the human eye in a way that the brain interprets as yellow.1324

The RGB color model relies on this principle, using red, green, and blue as primary colors. By varying the intensity of these beams, a wide gamut of colors can be produced; for instance, if the intensity of the green light is decreased or the red is increased, the resulting color shifts toward orange. If all three primary colors are combined in equal amounts, the result is white light.12