Which of the following colours of white light has the least wavelength?

Violet light has the least wavelength.
White light disperses into its seven constituent colours when it passes through a prism. In the white light spectrum, red has the longest wavelength and the least frequency (least deviation), whereas violet has the shortest or least wavelength and the highest frequency (maximum deviation) among all the colours in the visible spectrum. As we go from red to violet (top to bottom), the wavelength keeps decreasing while the frequency keeps increasing. Thus, violet would have the least wavelength among the given colours of light.