Students' misconceptions concerning colour phenomena and the apparent complexity of the underlying concepts--due to the different domains of knowledge involved--make its teaching very difficult. We have developed and tested a teaching device, the addition table of colours (ATC), that encompasses additive and subtractive mixtures in a single conceptual model and presents colour as a perceptual response to light. The ATC was used as the focus of an introduction to colour phenomena in a middle class setting, showing significant educational gains among the students.