How are colloidal solutions of gold prepared by different colours?

Different diameters of colloidal gold particles Variable valency of gold Different concentration of gold particles Impurities produced by different methods

Different diameters of colloidal gold particles

Colloidal solutions of gold prepared by different methods are of different colours because of different diameters of colloidal gold particles. The colour of colloidal solutions depends upon the size of the colloidal particles.