When white light travels through a prism the speed of this light is slowed down. Now there is a relation between speed of light, frequency and wavelength.
So when a red light of 700nm enters a prism it will slow down at 0,9c. So wavelength = speed / frequency. Now you can theoretically divide the changes. So 600nm = 0,9 / 0,0015 or you can have 800nm = 0,9 / 0,0011.
So the color in the prism can turns to 600nm or 800nm. Probably after leaving the prism the color gets back its original color.
But is it the case while travelling through the prism the color changes? Probably very tiny?