RGB Color Model: Mixing Light, Not Paint

WHY IT EXISTS: To create a standard system for devices that emit light, like screens, to reproduce a wide spectrum of colors. It models how colors can be created by combining primary light sources, which is fundamental for any digital display.

THE MENTAL MODEL: Think of mixing light, not paint. Imagine three spotlights—one red, one green, and one blue—shining on the same spot on a dark wall. Where only the red light hits, you see red. Where red and green overlap, you see yellow. Where all three overlap at full intensity, you see white. This is an additive process: you start with black (no light) and add light to create color.

HOW IT WORKS: The model defines any color as a combination of the three additive primary colors: red, green, and blue. Each color is produced by varying the intensity of these three primaries. For example, a bright yellow is created by mixing high-intensity red and green light with no blue light. A dim gray is created by mixing low, equal intensities of all three.

WHEN TO USE IT: The RGB model is the standard for any technology that creates color by emitting light. This includes computer monitors, smartphone and tablet screens, television sets, video projectors, and the sensors in digital cameras. It is the native language of digital graphics.

WHEN NOT TO USE IT: RGB is the wrong model for physical media that reflect light, such as ink on paper. Printing uses a subtractive color model (like CMYK), where inks absorb or 'subtract' wavelengths from the white light reflecting off the paper. Using an RGB profile for a print job will produce inaccurate, often muddy, colors.

ONE CANONICAL EXAMPLE: On a screen, pure red is displayed by activating the red light source at full intensity while the green and blue sources are off. Magenta is created by mixing full-intensity red and blue light with no green. White is the result of all three red, green, and blue light sources being at their maximum intensity.