Hex or hex code, short for hexadecimal code, refers to a system that uses the digits 0-9 and the letters A-F to represent colours. Each colour is assigned a unique six-digit code, with two digits each representing the amount of red, green, and blue (RGB) in the colour. For example, the hex code #FF0000 represents the colour red, with maximum amounts of red (FF) and no green or blue. Hex codes are widely used in HTML and CSS to e.g. specify the colours of text, backgrounds, borders and other elements on web pages.