Pigments played a vital technological role by enabling the development of advanced artistic techniques, preserving cultural heritage through durable materials like frescoes and facilitating innovations in early chemistry, such as the creation of synthetic colouring compounds. This paper examines pigments found in some exceptional Pompeian contexts spanning the 3rd century BCE to the 79 CE eruption, covering almost the entire palette of an ancient painter made of natural and synthetic, inorganic and organic pigments. Their composition has been revealed thanks to a non-invasive analytical approach designed to preserve these invaluable archaeological resources, illuminating that the artists skillfully mixed the colouring materials to achieve an uncountable range of colour tones. Quantifying any individual colouring compound enables a review of recipes as reported by ancient sources and modern scientific literature and opens new scenarios in the artistic process that likely started in the pigmentarium. In the analysis of the mixtures, the role of Egyptian blue and red lead in the variation of shades, which are almost ubiquitous as additional components in paint mixtures, is worth noting. Ultimately, one of the samples uncovered the earliest known use of a light green compound containing baryte and alunite, providing the first definitive evidence of barium sulphate being utilized in the Mediterranean during ancient times.
