I know that red and blue etc. lights are produced when 'white' light is put through mediums.
I have learned that all light in a vacuum, all electromagnetic waves, travel at the same speed in a vacuum. But, the blue light is traveling at a different speed to begin with, no? How is it exactly that red and blue light change speed in a vacuum to be the same and still be red and blue?
For instance, put two sources of light produces the right frequencies and , one blue and one red in a vacuum. Turn the sources on. How can red and blue still be 'red and blue' if they travel at the same speed? Or, are they NOT red and blue, they simple would go into the vacuum and become the same speed, and thus also not have 'color' (at least to our eyes)?
Also, can you please tell me why this is true?
Through the vacuum of space, no matter what their energy is, they always travel at the speed of light. It doesn't matter how quickly you chase after or run towards light, either; that speed you view it traveling at will always be the same. The thing that shifts, instead of its speed, will be the light's energy. Move towards light and it appears bluer, boosting it to higher energies. Move away from it and it appears redder, shifted to lower energies. But none of that, no matter how you move, how you make the light move, or how you change the energy, will cause the speed of light to change. The highest-energy photon and the lowest-energy photon ever observed both travel at exactly the same speed.
(From Ask Ethan: Does Light Always Move At The Same Speed? (Ethan Siegel, Forbes.com, Jul 29, 2017).