What is a Colour Space?

Colour space is a mathematical model that defines colours as tuples of numbers. Colour models have methods for creating some new colours from primary colours. Each colour space is different in every system (print, digital, video games etc) but for each case, there is always the appropriate colour space. A few examples of well know colour spaces are RGB (Red/Green/Blue), CMY (Cyan/Magenta/Yellow), CMYK (Cyan/Magenta/Yellow/Black)