Spectrum
The reason why the white light separates into in its component colors instead of remaining white is because the shorter wavelengths are refracted, or bent, more than the longer wavelengths.  Thus, red, having the longest visible wavelength, will appear closest to the line perpendicular to the surface of the material (the normal), that is, it will be bent the least.  Violet light, with the smallest wavelength  in the visible spectrum, will be bent the most.  The rainbow produced will always be in the same order: red, orange, yellow, green, blue, indigo, violet.