The intense examination of colour brought together Tim Otto Roth and Konrad Scheurmann more than ten years ago. At the end of the joint research project FARBAKS, directed by Scheurmann, the art historian had an extended conversation with the artist and researcher Roth, covering the spectrum of their collaboration. The dialogue, oscillating between the fields of arts and sciences, introduces various of Roth's artworks, examining colour's historical but also theoretical aspects. The artist explains his various approaches to colour as a phenomenon and epistemic object, based on his sound historical knowledge, which turns the interview into a survey on the contemporary status of colour research. The conversation culminates in a spectral revision confronting the reductionist human three-colour vision with a spectroscopic approach, dispersing light into the spectral bands of its constituent colours. Most of Roth's works can be considered as a plea for a “physics of art”, as they reveal the physical dimension of phenomena. The German artist collaborates regularly with scientific institutions and, as in the sciences, intrinsically artistic questions, as about the phenomenon of colour, are examined in a novel way. The affinity between art and science animated Roth to numerous projects – often in public space – collaborating with scientists of top research institutions around the world, such as the Max-Planck-Gesellschaft (Germany), TU Dresden (Germany), KIT Karlsruhe (Germany), the European Southern Observatory, ESA and NASA and the IceCube Neutrino Observatory in Antarctica.