Which of these pigments was not used in cave paintings?
Prehistoric peoples used a variety of natural pigments to make colorful paintings. They used minerals, crushed shells, clays, charcoal, and even bat guano to create different hues. These were then crushed on stones and mixed with water to form a paste. Notably, the colors blue and green have rarely been found in cave paintings, possibly reflecting the difficulty in finding pigments in these shades. Verdigris is a blue-green hue that forms from copper, brass, or bronze after prolonged exposure to air. It was first used in antiquity and the Middle Ages.
Source: Royal Society of Chemistry