Color Theory and Color Science

Color is the visual perception that results when light of different wavelengths reaches the eye. Visible light is a narrow band of the electromagnetic spectrum, with red at the long-wavelength end and violet at the short-wavelength end. Beyond the visible range lie infrared light, with wavelengths longer than red, and ultraviolet light, with wavelengths shorter than violet, neither of which the human eye can see directly. When white light passes through a prism or raindrops, it spreads into a spectrum, which is why a rainbow shows a continuous band of colors.

Color mixing follows two distinct systems depending on whether light is being added or removed. The additive system applies to sources that emit light, such as displays. Its primary colors are red, green, and blue (RGB), and combining all three in equal measure produces white. A color's RGB values describe how much of each primary is present. The subtractive system applies to inks, paints, and dyes, which work by absorbing some wavelengths and reflecting others. Its primaries are cyan, magenta, and yellow (CMY), and mixing them removes light, tending toward black.

Color perception is not a property of light alone but of how the eye and brain respond to it. The retina contains cone cells sensitive to different parts of the spectrum, and the brain combines their signals into the sensation of color. Because perception depends on this biological response, the same physical light can appear different under different conditions, and color science studies how to describe and reproduce color reliably.

Frequently asked questions

What is the difference between additive and subtractive color?

Additive mixing combines emitted light using red, green, and blue primaries and approaches white, while subtractive mixing uses pigments with cyan, magenta, and yellow primaries that absorb light and approach black.

Why are red, green, and blue chosen as additive primaries?

The human eye has three types of cone cells most sensitive to roughly these regions of the spectrum, so combining red, green, and blue light can produce a wide range of perceived colors.

Can people see infrared and ultraviolet light?

No. Both lie outside the visible spectrum — infrared has longer wavelengths than red and ultraviolet shorter than violet — so the human eye cannot detect them directly.