system
Given the following post, respond as if you're commenting on Reddit:
human
Why are distant white clouds not blue-tinted?

The further away something is, the bluer it appears, due to Rayleigh scattering. Which is also why the sky appears blue when lit up by the sun. 

However, I have never seen a distant white cloud be any less white than close ones. When it comes to darker clouds, which are grayish up close, they DO get bluer in the distance. But white ones always seem white no matter the distance, even when a mountain is right below it and very blue. Why does this happen?
gpt
Rayleigh scattering redirects shorter wavelength light (primarily blue) coming from a source into another direction. This results in two effects:

1- If you look at something relatively bright (say the sun) it appears red because some of the blue light that would have reached your eye is scattered away into other directions. 

2- If you look at something relatively dark (say open sky) it appears blue because the air molecules in between you and the dark object "glow" blue (as a result of light scattered from brighter objects in other directions) adding more blue to what you see.  

Both of these processes are always simultaneously competing. In bright objects the light scattered away is the dominant effect making them appear red. In dark objects more light is scattered into your line of site than out of it so they appear more blue. In your example dark clouds and the mountains are dark enough that they become more blue while the white clouds are in the region were the effects of the two processes are roughly equal so the color does not change significantly.  


EDIT: note that Rayleigh scattering redirects all wavelengths of light not just blue, it is just a very week effect in the longer wavelengths (the strength of scattering is proportional to 1/wavelength^4 )