How does the deviation produced by a triangular prism depend on the colour (or wavelength) of light incident on it ?

Deviation of light in a medium depends on the wavelength of light which is inversely proportional to the corresponding refractive index for that light in medium.

For example- violet light deviates the most in a medium while red the least because for violet light wavelength is least so refractive index is maximum due to which deviation produced is maximum.For red light wavelength is maximum so refractive index for a medium is minimum so deviation produced is minimum.

Deviation produced for all other colours of visible light lies between these two colours