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.
Which color of light travels fastest in a vacuum?
What can you say about the speed of the different colors of light in air?
Speed of light is constant only in vacuum, once it enters any medium such as air it actually depends on its refractive index. The refractive index of air (around 1.0003) is very close to vacuum (1). Thus blue light will be very slightly slower than red light in air.
Why does light travel in a vacuum?
In contrast, light waves can travel through a vacuum, and do not require a medium. In empty space, the wave does not dissipate (grow smaller) no matter how far it travels, because the wave is not interacting with anything else. In this case, some light is absorbed and lost as heat, just like sound.
Why is the speed of light different in different mediums?
Speed of light does not change, it has to travel more in a medium than in vacuum, When light is passing through a medium, the electrons in the medium absorbs the energy from the light and gets excited and releases them back. The only reason why a photon can travel at light speeds is because it is mass less.