The planet Uranus is colored cyan because of the abundance of methane in its atmosphere. Methane absorbs red light and reflects the blue-green light which allows observers to see it as cyan. [22]

Cyanotype, or blueprint, a monochrome photographic printing process that predates the use of the word cyan as a color, yields a deep cyan-blue colored print based on the Prussian blue pigment. [24] Henry George Liddell, Robert Scott, A Greek-English Lexicon, κύαCyanosis is an abnormal blueness of the skin, usually a sign of poor oxygen intake; patients are typically described as being "cyanotic". [27] Cyan ( / ˈ s aɪ . ə n, - æ n/) [1] [2] [3] is the color between blue and green on the visible spectrum of light. [4] [5] It is evoked by light with a predominant wavelength between 490 and 520 nm, between the wavelengths of green and blue. [6] cyan". Oxford English Dictionary (Onlineed.). Oxford University Press. (Subscription or participating institution membership required.) Colors in the cyan color range are teal, turquoise, electric blue, aquamarine, and others described as blue-green. Cyan is most often associated with peace, relaxation, healthcare, dreams, and spirituality.

In the subtractive color system, or CMYK color model, which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta and yellow. In the additive color system, or RGB 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. Mixing red light and cyan light at the right intensity will make white light.While both the additive secondary and the subtractive primary are called cyan, they can be substantially different from one another. Cyan printing ink is typically more saturated than the RGB secondary cyan, depending on what RGB color space and ink are considered. That is, process cyan is usually outside the RGB gamut, [18] and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed color that is pure cyan ink. This is because real-world subtractive (unlike additive) color mixing does not consistently produce the same result when mixing apparently identical colors, since the specific frequencies filtered out to produce that color affect how it interacts with other colors. Phthalocyanine blue is one such commonly used pigment. A typical formulation of process cyan is shown in the color box on the right. The web color cyan shown at right is a secondary color in the RGB color model, which uses combinations of red, green and blue light to create all the colors on computer and television displays. In X11 colors, this color is called both cyan and aqua. In the HTML color list, this same color is called aqua. Pure water is nearly colorless. However, it does absorb slightly more red light than blue, giving significant volumes of water a bluish tint; increased scattering of blue light due to fine particles in the water shifts the blue color toward green, for a typically cyan net color. [19] Cyanopsia is a color vision defect where vision is tinted blue. This can be a drug-induced side effect or experienced after cataract removal.