Colour is a set of attributes and perceptions related to the wavelengths of light. It is often described through sets of primary colours (blue, red and yellow) such as RGB and set of combinations of primary colours, like orange, green, purple. In decribing food products often three scales are used; from white (L*) to black; from green (-a*) to red (+ a*) and from blue (-b*) to yellow (+b*).
Colour categories, or physical specifications of color, are associated with objects through which different wavelengths of various intensities of light is reflected and/or dispersed. This is governed by the object’s physical properties and the physical properties of light such as absorption, emission spectra, phase velocity, etc.