Light does not need any medium for its propagation. It can even travel through a vacuum.
The speed of light in vacuum or air is, c = 3 × 108 ms-1
Since light is in the form of waves, it is characterized by a wavelength (λ) and a frequency (v), which are related by the following equation: c = vλ (c = velocity of light).
Different coloured light has a different wavelength and frequency.