In order to give his students an example of underpainting, the french artist jean-auguste-dominique ingres created an entire painting in gray values. this type of gray underpainting is referred to

The correct answer is Grisaille

It consists of a painting technique that underpaints many layers of grey paint or another grayish color, which will define the relationship between the other colors in the composition. Usually is used to imitate sculptures in decorative schemes. The same technique can be used with other under painted colors, like green (verdaille) and brown (brunaille).

Explanation:

Grisaille can be used as underpainting not only with oil paint, as Rubens used it as a  model to work with his engravings because of the effects of those monochrome compositions, which details can be noticed more easily.  

Giotto considered one of the fathers of the Renaissance Style, first used the grey underpainting in the Scrovengi Chapel (circa 1304), in Padua. But this tradition continued mostly in the Netherlands, where it started in the Dutch Renaissance and had its climax in Rembrandt’s and Frans Hals’artworks.

Ingres, Poussin, David, and Jerôme were the masters of Neoclassical painting, a style that has reached the overseas, mainly because this classical revival was the one adopted by the Arts Academy during the passage from the 18th to the 19th century.

The Neoclassical consisted in a return to the techniques presented in the classics models, and the rereading of the mythology associated with the image of the Emperors.

Basically, Ingres has used the grisaille to compose the sculptural backgrounds, where he could depict magnificent and enormous compositions, everything based on Renaissance ideal beauty. He was one of Napoleon’s court painters and has created a lot of paintings during that imperial reign.

In Modern Art, a great example is Pablo Picasso’s Guernica (1937) that is a whole composition working with the greyscale. Hugo Bastidas used it in his photograph-based paintings, which gave them a phot-realistic effect.