Why does a secondary rainbow have inverted colours ?

Explanation

Colliodal solutions are generally coloured on account of the scattering of light by the particles of the dispersed please i.e., colloidal particle. Since the particles present in different colloidal solutions differ in sizes, they impart specific colours to these solutions on passing light. The coloure of the gold sol containing very fine particles of gold is red. As the particle size increases, the colour of solution changes to purple, blue and finaly becomes golden yellow. As the particle size changes, the wavelength of the scattered light also changes resulting in different colours.