Robert Grosseteste and the Colours

Here we discuss the De Colore, one of the short scientific treatises written by Robert Grosseteste in the mid-1220s. In this treatise, Grosseteste continues the discussion on light and colours he started in the De Iride. The medieval scientist describes two manners of counting colours: one gives an infinity of tones, the other counts seven essential colours. In both cases, colours are created by the purity or impurity of the transparent medium when light is passing through it. This was the medieval explanation of colours that survived until Newton’s experiments with prisms.