Cyan is the colour of shallow water over a sandy beach. The water absorbs the colour red from the sunlight, leaving a greenish-blue colour.

Cyan is the colour halfway between blue and green on the colour wheel. It is one of the primary (main) colours of ink in an inkjet printer, along with magenta, yellow and black. 

Cyan is a secondary colour of light, along with magenta and yellow. The primary colours of light are: blue, red and green (RGB). Cyan is made by mixing green and blue light.