Verdaccio

Verdaccio is an Italian name for the mixture of black, white, and yellow pigments resulting in a grayish or yellowish (depending on the proportion) soft greenish brown.

Verdaccio became an integral part of fresco painting, in which this color is used for defining tonal values, forming a complete monochromatic underpainting. Often architectural details in frescoes are left in verdaccio without any additional color layers; a notable example is the ceiling of the Sistine Chapel, where verdaccio underpainting can be clearly seen, left as it is on all architectural details of the composition.