We’re very pleased to announce the publication of our latest collaborative investigation into the rainbow, ‘Color-coordinate system from a 13th-century account of rainbows’ which has come out in the Journal of the Optical Society of America A, 31 (2014), A341-A349. The article explores colour within the 3D framework set out in Grosseteste’s De colore and now links the axes of variation to observable properties of rainbows, as Grosseteste indicates. Modern understanding of the physics of rainbows and of human colour perception are deployed to help resolve some of the linguistic ambiguities of the medieval text and to interpret Grosseteste’s key terms. As Tom observed at Christmas, the combination of expertise required to make the connections and explanations in the paper is startling, from Philip Laven’s work on rainbows, to Bob Fosbury’s work on atmospheric pollutants, Phil Anderson’s experience from polar and marine physics, alongside Hannah’s conception as to how the two treatises mapped and how the spiral rainbow plot gives, literally and conceptually, shape to the investigation, and Tom and Brian’s sharp-eyed calculations. This went alongside an involved discussion from the humanities side on the precise meaning of colour-terms in the ancient and medieval thought-systems, and how very difficult it is to translate and apprehend what they actually meant. It is the combination of these skills that enables Grosseteste’s text to be seen from such a different and powerful perspective.