This is interesting:

Why can't the human eye focus blue light?

biology.stackexchange.com›why-cant-the-human-eye-focus-blue-light Light is scattered by gas molecules in air. The shorter the wavelength of light, the more it is scattered by the atmosphere. Because it has a shorter wavelength, blue light is scattered ten times more than red light. One reason is that blue light has a frequency that is closer to the resonant frequency of atoms than e.g. red light (Exploratorum). Due to this scattering the eye and lasers have difficulty focussing as object edges get fuzzy.The scattering of blue light degrades vision in normal day light, especially in foggy conditions when light scattering is at its worst due to the droplets of water in the air. Yellow filters (for example yellow sports sunglasses) improve visual acuity by filtering out the aberrant blue light (Laramy-K Optical). Fun fact The predominant scattering of blue light makes that the sun is clear in the sky as a yellowish circle, while the sky is blue due to the fact that it is the blue light predominantly being scattered away from the sunlight. biology.stackexchange.com›why-cant-the-human-eye-focus-blue-light