The colours on their palettes would have been made from the best of pigments. Earth pigments, such as red and yellow ochres, were cheap and easily obtainable. Other more costly pigments were often purchased for specific commissions.
The most stable pigments for fresco painting were ochres, green earth (terre verte), Egyptian blue and vermilion and most paintings consisted of these.
Cinnebar, an expensive red pigment, was found to have been used in the impressive painting in the substantial bath-house in Southwark. This architectural scene can be seen in a restored state in the Roman London gallery.
White was often added to pigments to allow better cover. White pigment would have been made from white lead, chalk or ground oyster shells while black was obtained from soot or charcoal and mixed with size.
Egyptian blue was a pigment artificially prepared from copper, silica and calcium. Other colours, such as indigo and purple, were made from vegetable dyes added to other mediums to make them usable as pigments.