How an opaque body takes the colour of what faces it
Light and shadow on a surface a b lit between a bright object c d and a dark object e f
With a small ray diagram in the upper right, Leonardo states that the surface of every opaque body partakes of the colour of the object facing it, and does so more strongly where it lies nearer to that object. He works the case through with letters: given an opaque body a b lit on one side by a luminous object c d and on the other by a shadowy object e f, the middle of the body shares equally in both, the part a o is more luminous than the part o b, and the surface grows brighter the nearer it lies to the light and darker the nearer it lies to the shadow. The reasoning belongs both to the physics of light and shadow and to the painter's doctrine of reflected colour.
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A surface shares the colour of the object facing it
The surface of every opaque body partakes of the colour of the object facing it, and most where it lies nearest that object. For an opaque body a b set between a luminous object c d and a shadowy object e f, the middle shares equally in both, part a o is more luminous than part o b, and the surface grows brighter toward the light and darker toward the shadow.
Reflected colour as a rule for the painter
The claim that a lit surface takes on the colour of neighbouring bright and dark objects, in proportion to nearness, states the painter's principle of reflected light and colour on a form.