Cyan is a greenish blue colour. It is evoked by light with a predominate wavelength of between 490 - 520 nm , between the wavelengths of green and blue.
In the subtractive colour system , or CMYK ( subtractive ) which can be overlaid to produce all colours in paint and colour printing , cyan is one of the primary colours along with magenta , yellow and black.
In the additive colour system , or RGBC ( 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 compliment of red , it can be made by the removal of red from the white light.
Mixing red light and cyan light at the same intensity will make white light. The web colour cyan is synonymous with aqua.