OF LIGHT AND SHADE.
Every portion of the surface of a body is varied [in hue] by the [reflected] colour of the object that may be opposite to it.
EXAMPLE.
If you place a spherical body between various objects that is to say with [direct] sunlight on one side of it, and on the other a wall illuminated by the sun, which wall may be green or of any other colour, while the surface on which it is placed may be red, and the two lateral sides are in shadow, you will see that the natural colour of that body will assume something of the hue reflected from those objects. The strongest will be [given by] the luminous body; the second by the illuminated wall, the third by the shadows. There will still be a portion which will take a tint from the colour of the edges.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.