Quotation from: The Notebooks of Leonardo Da Vinci

Written by: Leonardo da Vinci

463.

OF LANDSCAPES.

The colours of the shadows in mountains at a great distance take a
most lovely blue, much purer than their illuminated portions. And
from this it follows that when the rock of a mountain is reddish the
illuminated portions are violet (?) and the more they are lighted
the more they display their proper colour.