The Da Vinci Notebooks at sacred-texts.com
The shadows of verdure are always somewhat blue, and so is every shadow of every object; and they assume this hue more in proportion as they are remote from the eye, and less in proportion as they are nearer.
The leaves which reflect the blue of the atmosphere always present themselves to the eye edgewise.
The illuminated portion, at a great distance, will appear most nearly of its natural colour where the strongest light falls upon it.