The Colour Wheel can be described as an abstract illustrative organization of colour hues around a circle that shows relationships between primary colours, secondary colours, complementary colours, etc.
Traditionally colours are represented on a wheel of 12 colours three primary colours, three secondary colours (created by mixing primary colours) and six tertiary colours (created by mixing the primary and secondary colours).
Artists use a traditional colour wheel based on the Red/Yellow/Blue model with secondary colours of orange, green and purple. For all computer-based colour, a wheel based on the RGB model is used; this encompasses the CMY model as well since cyan, magenta and yellow are the secondary colours for red, green and blue. (Conversely the secondary colours for cyan, magenta and yellow are red, green and blue.) In the RGB/CMY colour wheel, orange is a tertiary colour between red and yellow and purple is a tertiary colour between magenta and blue.