Which Colour of light travels fastest in glass?
Violet light has the shortest wavelength and is bent the most.
Thus violet light travels more slowly through glass than does any other color and red light travels fastest.
Which travels more slowly in glass red light or violet light why?
Because of the Refractive Index  violet light travels slower through glass, than red light. Red light possess the biggest wavelength in the optical spectrum, but it also carries less energy. While violet light has the shortest wavelength, but carries the biggest amount of energy.
Why does a prism break light up into colors?
Dispersive prisms are used to break up light into its constituent spectral colors because the refractive index depends on frequency; the white light entering the prism is a mixture of different frequencies, each of which gets bent slightly differently.
Do different colors of light travel different speeds?
In empty space, all colors travel at the same speed called c. Light of different wavelengths, or colours, travels at different speeds when they travel through any medium other than vacuum. Red light travels faster than blue in glass.