The other day I read an article posted in the Science section of Forbes.com. The title was “Earth’s skies are violet, we just see them as blue“. It explained how the different colours of light scatter differently in the Earth’s atmosphere according to their wavelength, with shorter blue light scattering most which is why the skies seem blue, but then goes on to point out that violet light has an even shorter wavelength than blue so our skies should look violet. Why don’t they? Well, it’s because our eyeballs have three kinds of colour light detector in them. We call these detectors “cones” and each is most sensitive to either blue, red or green (most sensitive to, not only sensitive too) – the blue stimulates most so the skies look blue….
But, wait! Look at this from the other day here (no “post-processing” going on – just as I actually saw it)
Skies look blue, except when they don’t…….(thank you, clouds)
Heroes Not Zombies 
May I use this (with credit to you) as my Facebook background image? It’s stunning.
Sure, you’re welcome. Glad you like it and thanks for asking 😃
thank you so much