Why do distant mountains look blue or purple?
This happens due to the Rayleigh scattering effect. The light is scattered among the air molecules and the shorter wavelength (blue) disperses out the furthest, so we see a blue tint.
because normally the sun is setting and that causes it.
The sun causes that to happen just like how the ocean looks blue but it's really clear.
of the sun
Its the sun.I know that because i see blue-ish mountains.It probably the reflection of the sun on the mountains.