The human perception of colours. For demonstrating that white light is composed from all the spectral colours by rotation of multi-colored disc. Comprising a multicoloured circular disc of dia 150 mm diameter approx.,is attached to a pulley mounted on a metal/plastic base driven by a belt with the help of a hand driven wheel having sectors of various spectral colour in proper proportions. On rotating the disc at sufficient speed, all the colours will be observed to disappear by merging into a single white colour. Complete assembly mounted on a stable base.