The perception of a picture or a color stays in the human brain for a fraction of a second. Newton's color disk is a mechanical device that rotates an array of colors arranged as petals or gradients around an axis and when the disc rotates fast enough the perception of the color changes to white. This is because white light is nothing but the mixture of light of all wavelengths in the visible range.
Sir Isaac Newton used this device to prove the above assertion that white color is the mixture of all colors.
So Light is not colourless.
