Vol. I: VIII. Botany for Painters and Elements of Landscape Painting: 422.
The Da Vinci Notebooks
The accidents of colour in the foliage of trees are 4. That is: shadow, light, lustre [reflected light] and transparency.
These accidents of colour in the foliage of trees become confused at a great distance and that which has most breadth [whether light or shade, &c] will be most conspicuous.