In Newton ’ s day , people still believed that colour was a mixture of light and darkness , and that prisms somehow “ coloured ” light . Realizing that this theory was false , Newton set up a prism near his sunlit window , and projected a rainbow of colours onto
a wall 22 feet away . To prove that the prism was not itself colouring the light , he refracted the light back together through a second inverted prism . Newton is therefore credited with identifying the colours that make up the visible spectrum - or rainbow .
Newton believed that the rainbow of colours shared a harmonious relationship . He figured that just as the sound of a ringing bell or a musical string creates waves that travel through the air and are sensed by our ears , so also do the rays of light reflecting from an object create waves that our eyes see as colours .
This is clearly reflected in Newton ’ s colour circle which shows the seven colours correlated to the seven musical notes . The spectral colours , from red to violet , complete a full octave , from D to D .
In a musical scale of seven notes , individual notes can be combined to create new chords and harmonies . Just like musical notes , Newton believed that the coloured light waves could be combined harmoniously to create new colours .
Wrapping the colour spectrum into a circle became the model upon which future colour systems and colour wheels would be based .