Cyan is a greenish-blue color. It is evoked by light with a predominant wavelength of between 490–520 nm, between the wavelengths of blue and green.

In the subtractive color system, or CMYK (subtractive), which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta, yellow, and black. In the additive color system, or RGB (additive) color model, used to create all the colors on a computer or television display, cyan is made by mixing equal amounts of green and blue light. Cyan is the complement of red; it can be made by the removal of red from white light. Mixing red light and cyan light at the right intensity will make white light.

The web color cyan is synonymous with aqua. Other colors in the cyan color range are teal, turquoise, electric blue, aquamarine, and others described as blue-green.