In contrast to the glazing technique of oil painting, tempera-based media as manuscript illumination and portrait miniature painting created colour hues mainly by a physical mixture of pigments or dyes on the painter’s palette. The mixture ratio of painters advanced ideas about a colour specification system that could be used to specify the colour of any coloured object. Therefore, I will focus on the relation between portrait miniature painting and 17th-century scientific experiments on colour, looking into models of colour gradation and colour scales. For a long time, miniature painting lingered between the realm of goldsmithery and painting – thus combining an interest in colours in nature (gems) and colours in art (pigments).