The main characteristic of white is that it’s a neutral colour that can be either warm or cool depending on its shade. It has the unique ability to enhance or vary the intensity of another colour.
The first is physical: this is the additive system, which refers to light. According to this system, white is the origin of the prism of light from which all the colours are created. Therefore, their addition reconstitutes the white.
The second is more pictorial: this is the subtractive system, which considers white to be achromatic (having no colour). According to this system, white is the absence of colour or, more generally, the colour of the medium.
It can be glossy or matt, light or saturated, bright or dull… a great asset that has tempted many an artist! Kasimir Malevitch pushed it to the limits of minimalist abstraction with his White on White; and Roman Opalka worked for years on an incredible approach with his piece Details, an increasing sequence of numbers painted on white canvases.
So, even though Newton stated that white wasn’t a colour (for him, it was much more), let’s agree that it’s an essential part of every creation!