1. Physicists explain colour as a function of light. This is the Additive model. White light was first proven to contain all of the colours by the physicist Sir Isaac. The light primaries are different from the pigment primaries. The secondaries colours are red, green and purple. The primaries colours are magenta, cyan and yellow.
2. When you want to pain with pigments, you use the subtractive model, in other words, the CMYK model, CYAN, MAGENTA, YELLOW and BLACK, the colour that results of mixing all of them.
CYAN + YELLOW = GREEN
YELLOW + MAGENTA = RED
MAGENTA + CYAN = PURPLE
MORE CYAN + MAGENTA = INDIGO
MORE MAGENTA + CYAN = MAUVE
YELLOW + MAGENTA + CYAN = BLACK