What colours make black? What colours make white?
The way to create black or white depends on whether you’re working with an additive colour model (light-based) or a subtractive colour model (ink-based).
Additive colours combine to create white.
Light and electromagnetic radiation both create additive colour. In this model of colour theory, the combination of all colours creates the perception of white. You’ll also hear this model referred to as RGB, because when you work with additive colour, you use red, green and blue as primary colours.
Digital colour is additive.
Additive colour is used in digital design, because computer screens show hues with coloured light. Each pixel is composed of three tiny specks of phosphor, which emit red, green or blue light when struck by an electron beam. When working with colour digitally, like in Adobe Photoshop or Illustrator, your screen uses different combinations of these lights to create all the colours you see. So what is black on a screen? No lit phosphors.
Subtractive colours combine to create black.
The colour of pigments and inks are subtractive. Subtractive colours are made of light that’s already passed through material. Painters can combine several colours to make what looks like black paint. Printing also uses subtractive colours; cyan (C), magenta (M), yellow (Y) and key or black (K) are the primary inks used. This is why printable files are called CMYK files.