Which one is not a primary colour in painting?

The correct answer is Option (2) → Green

Primary colours are the colours that cannot be made by mixing other colours, while every other colour can be mixed from them. In painting, the three primary colours are red, yellow and blue.

Green is a secondary colour: a painter gets it by mixing blue and yellow paint.

Tip: The primary colours of light are different: red, green and blue. Mixing coloured lights adds them up, while mixing paints takes colours away, so the two sets differ.