Cyan (/ˈs.ən/ or /ˈs.æn/) 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 colours in paint and colour printing, cyan is one of the primary colors, along with magenta, yellow, and black. In the additive color system, or RGB (additive) colour model, used to create all the colours 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 on a black screen will make white.

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

Etymology

Its name is derived from the Ancient Greek κύανος, transliterated kyanos, meaning "dark blue". It was formerly known as "cyan blue" or cyan-blue, and its first recorded use of as a colour name in English was in 1879. Further origins of the colour name can be traced back to a dye produced from the cornflower (Centaurea cyanus).

In most languages, 'cyan' isn't a basic color term and it phenomenologically appears as a greenish vibrant hue of blue to most English speakers. Reasons for why cyan isn't linguistically acknowledged as a basic colour term can be found in the frequent lack of distinction between blue and green in a large number of languages.

Cyan on the web and in printing

The web colours cyan and aqua

The web color cyan shown at right is a secondary colour in the RGB colour model, which uses combinations of red, green and blue light to create all the colours on computer and television displays. In X11 colors, this colour is called both cyan and aqua. In the HTML colour list, this same colour is called aqua.

The web colours are more vivid than the cyan used in the CMYK colour system, and the web colours can't be accurately reproduced on a printed page. To reproduce the web colour cyan in inks, it is necessary to add a few white ink to the printer's cyan below, so when it is reproduced in printing, it isn't a primary subtractive color. It is called aqua (a name in use after 1598) because it is a colour commonly associated with water, such as the appearance of the water at a tropical beach.

Process cyan (pigment cyan) (printer's cyan)

Cyan is additionally one of the common inks used in four-color printing, along with magenta, yellow, and black; this set of colours is referred to as CMYK as in spectrum(s).

While both the additive secondary and the subtractive primary are called cyan, they can be substantially different from one another. Cyan printing ink can be more saturated or less saturated than the RGB secondary cyan, depending on what RGB colour space and ink are considered.

Process cyan isn't an RGB color, and there's no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed colour that's pure cyan ink. This is because real-world subtractive (unlike additive) colour mixing doesn't consistently produce the same result when mixing apparently identical colors, after the specific frequencies filtered out to produce that colour affect how it interacts with additional colors. A typical formulation of process cyan is shown in the colour box at right.

In science and nature

Color of water

  • Pure water is nearly colorless. Notwithstanding it does absorb slightly more red light than blue, giving large volumes of water a bluish tint; increased scattering of blue light due to fine particles in the water shifts the blue colour toward green, for a typically cyan net color.

Cyan and cyanide

Bacteria

Astronomy

Energy

Photography and film

  • Cyanotype, or blueprint, a monochrome photographic printing process that predates the use of the word cyan as a color, yields a deep cyan-blue coloured print based on the Prussian blue pigment.
  • Cinecolor, a bi-pack colour process, the photographer would load a standard camera with two films, one orthochromatic, dyed red, and a panchromatic strip behind it. Color light would expose the cyan record on the ortho stock, which additionally acted as a filter, exposing only red light to the panchromatic film stock.

Medicine

  • Cyanosis is an abnormal blueness of the skin, usually a sign of poor oxygen intake. i.e. the patient is "cyanotic".
  • Cyan is associated with the throat chakra in vedic medicine.

Surgeon gowns

  • In the nineteenth century, surgeons wore white gowns, but in the twentieth century surgeons began to wear cyan or green surgical gowns, for several reasons. First, in the brightly lit operating room, cyan reflected less light than white and caused less strain on the eyes of the medical team. Second, cyan is the complementary color of red, so red blood on a cyan gown looks black or grey rather than red, and isn't as vivid. Also, shifting your sight to cyan after staring at red for long periods of time doesn't cause cyan after-images, as shifting from red to white will do. Lastly, after cyan is considered a restful and soothing color, it causes less anxiety to patients.

In human culture

Architecture

  • Cyan coloured tiles are often used to pave swimming pools to make the water within them seem more intensely colored, and therefore more inviting.

Video Games