The school promotes the unique value of colours in Sicily. It was Newton who discovered that white light is a mixture of colours like those of the rainbow. But what light is made of, nobody had understood until 1848, when James Clerk Maxwell came up with his famous equations. Incredible but true: light is produced by making electric charge oscillate extremely rapidly. These oscillations produce two incredibly evanescent quantities: the electric field and the magnetic field. Quantities that cannot be detached from each other. Quantities that need no medium to propagate. Light from the Sun reaches us after passing through 150 million kilometres of vacuum. On a starry night, the light that reaches the retina of our eyes has crossed billions and billions of kilometres of emptiness. The emptier the space, the better the light propagates. Goethe had his own ideas about light. And he refused to believe Newton’s discovery. For Goethe, colours were a purely subjective fact. Today we know about light that it is closely linked to so-called ‘weak’ forces, forces that act as a safety valve for the Sun’s nuclear fire. It took almost a hundred years to get to the bottom of it. Nobody had imagined that that safety valve could have any connection with light. Today, we know that electromagnetic forces (which generate light) and weak forces (which control nuclear combustion in the Sun) are closely linked. The writer has studied many aspects of this link. In short, the physical nature of light is understood better than any other Galilean phenomenon. The physiological, aesthetic, and artistic-pictorial properties of light, on the other hand, are all to be understood. Colours fascinated our ancestors before, long before, their physical properties were understood. And indeed, the art of colour has developed over millennia in a totally empirical manner. It is linked to the physiological effects produced by colours. A few examples. Shadows can appear not only grey but also coloured. Two colours observed at the same instant influence each other. Colour sensations persist even after the image has disappeared. They are phenomena related to what happens in the retina of our eyes. And to the signals it transmits to our brain. Much has been understood about the functioning of our eyes. For example: why the crystalline lens ages. But the ‘physiological’ nature of colours must give way when ‘aesthetics’ comes into play. How colour harmony comes about no one knows. The link between the different perceptions each of us possesses when putting different colours together is still to be understood. Why does someone like a mixture of colours and someone else a totally different combination? What is the physico-chemical- neurophysiological root that leads us to identify a set of colours linked to different symbols and shapes as a ‘work of art’? According to Wassily Kandinsky, each colour has an actual existence. Yellow is active, blue passive, green neutral, white motionless with hope, black motionless without hope, red agitated. Harold Baumbach, the American master painter of colour abstraction, was considered the explorer of colours. In colours lies a remarkable part of the mysteries related to the formidable electromagnetic structure of which we are the exclusive owners, the ‘on-board computer’ of the human machine: our brain. We have understood almost everything about the strictly scientific nature of light. However, there is still much to be understood about what can happen to our eyes, even if many of their properties have been understood. At the top of the global issues, however, are colours, which invite us to reflect on the ‘on-board computer’: the one truly responsible for their artistic-pictorial nature. Of the ‘on-board computer’ we can only say that it will always be a source of admiring devotion for those who gave it to us. Proof of this is the fascination of the colours associated with the land of Sicily, its panoramas, its sunrises, its formidable sunsets, and the spectacle of the extraordinary horizons lost between land, sky and sea.