We know that when white light passes through a diffraction grating it spits into a band of seven colors or spectrum which includes the color in the order VIBGYOR that stands for Violet, Indigo, Blue, Green, Yellow, Orange and Red respectively.
Red light has the longest wavelength and is least scattered whereas Violet light with the shortest wavelength is the one to get most scattered and as we move far from bright spot at the center, there is an increase in the wavelength of light, thus the color that corresponds to the closest one is Violet with the shortest wavelength in the band.
