A Treatise on Painting/Chapter 276
Chap. CCLXXVI.—Of the Surface of all shadowed Bodies.
The surface of any opake body placed in shadow, will participate of the colour of any other object which reflects the light upon it. This is very evident; for if such bodies were deprived of light in the space between them and the other bodies, they could not shew either shape or colour. We shall conclude then, that if the opake body be yellow, and that which reflects the light blue, the part reflected will be green, because green is composed of blue and yellow.