Colour of shadows and the beauty of shaded bodies
Set green near green shadows; where a colour shows its greatest brightness
A page of the Treatise on Painting arguing that the surface of every shadowed body takes on the colour of the objects near it, so the painter must place green things (meadows and the like) beside the shadows of green bodies lest their shadow degenerate into another hue. Two short chapters follow: one holds that a colour without luster shows its finest beauty in the brightest illuminated part of the body, the other explains that the edges of shaded bodies look lighter or darker than they are according to whether the neighbouring ground is darker or brighter. The whole sheet is continuous text with no drawing.
On this page
Match a shadow's surroundings to keep its true colour
Because every shadowed surface partakes of the colour of its object, the painter should set green things such as meadows beside the shadows of green bodies. Otherwise the shadow, borrowing colour from a red or other object placed opposite it, degenerates into a very ugly hue unlike the true shadow of green.
A colour is most beautiful in its brightest lit part
Chapter 768 states that the excellent beauty of any colour lacking luster always lies in the brightest illuminated part of the shadowed body. The finest showing of the hue is therefore in the light, not the shadow.
Edges look lighter or darker against their ground
Chapter 769 explains that the boundaries of shadowed bodies appear brighter or darker than they truly are in proportion as the neighbouring ground is darker or brighter than the body's own colour. The contrast at the edge, not the edge itself, produces the effect.