The Green of Leaves and the Darkness of Trees Against the Sky
Yellow and blue always make green; viewing foliage toward and away from the sun
This page sets out several short chapters on the appearance of foliage. Leonardo states the rule that yellow mixed with blue always makes green, and that the highlights of dense dark leaves behave increasingly like mirrors and so take on more blue. He observes that the loveliest greens appear where leaves interpose their thickness between the eye and the air, that a tree is much darker where it meets the sky than where it meets woods or hills, and he contrasts how plants look when viewed toward the sun (transparent, bright green at the edges) versus away from it (few shadows, many highlights).
On this page
Yellow mixed with blue always generates green
If the highlights of young leaves are generated by the blue air mirrored in them, those highlights will be green, by the rule that yellow colour mixed with blue always generates green. The highlights of all dense-surfaced leaves partake of the colour of the air, and the darker the leaves the more they behave as mirrors, so their highlights partake the more of blue.
The most beautiful greens and the darkest part of a tree
The most beautiful greens that tree leaves show occur where they interpose their thickness between the eye and the air. Much darker is that part of the tree which terminates against the sky than the part which terminates against a wood, mountains or hills.
Foliage viewed toward the sun versus away from it
When plants are viewed toward the sun, the transparency of their leaves makes the edges show a more beautiful green while the middle appears very dark, and the non-transparent leaves show their front and take very evident highlights. Viewed from the side opposite the sun, dense plants appear with few shadows and many highlights.