In 1931 (Commission Internationale de l’Eclairage (CIE) established the X-Y-Z tristimulus system for measuring colour properties, based on the assumption that every colour is a combination of three primary colors: red, green and blue. The CIE Chromaticity Diagram is a two dimensional colour space that defines all of the colours perceived by the human eye. Pure colours are located on the extreme outer edges of the diagram and white is located near the centre.