"From 1670 to 1672, Newton lectured on optics. During this period he investigated the refraction of light, demonstrating that a prism could decompose white light into a spectrum of colours, and that a lens and a second prism could recompose the multicoloured spectrum into white light. He also showed that the coloured light does not change its properties by separating out a coloured beam and shining it on various objects. Newton noted that regardless of whether it was reflected or scattered or transmitted, it stayed the same colour. Thus, he observed that colour is the result of objects interacting with already-coloured light rather than objects generating the colour themselves. This is known as Newton's theory of colour." "Newton argued that light is composed of particles or corpuscles, which were refracted by accelerating toward the denser medium, but he had to associate them with waves to explain the diffraction of light (Opticks Bk. II, Props. XII-L). Later physicists instead favoured a purely wavelike explanation of light to account for diffraction. Today's quantum mechanics, photons and the idea of wave–particle duality bear only a minor resemblance to Newton's understanding of light." Source and further information: http://en.wikipedia.org/wiki/Isaac_Newton#Optics

Sir isaac newton fond that a white light is made up of 7 basic colors {vibgyour} of different wave lengths. In order to prove this he rotates the 7 colour band disc with a speed of 44.6 m/sec he saw that in the of rotating the colourfull cd becomes white.