could relativity proof have been falsified?

[SEE]

Refraction of light through a gas and liquids is caused by a change of speed. We see a 'rainbow' effect because each wavelength (in the spectrum of light) the speed is affected differently and splits.

However, If all the wavelengths that make the spectrum of light were to bend at the same speed then refraction will not occur. This is probably why atmospheric interference was discounted.