The theory of colour is one of the most important aspects of applied optics and yet very few of us are fortunate enough to encounter it in highschool physics are even at university. This website provides a brief description of colour theory of light from light sources over object interaction to the human eye and finally visual perception. The first three sections on arts, physics and psychophysics describe the three general aspects of the theory. Under demonstration you can find the outline for a demo that can be easily constructed and show in grade 11 or 12 science classes. The apparatus is easy to build and requires only a modest investment of time and money. At the same time the apparatus allows for the demonstration of quite counter-intuitive aspects of colour mixing as well as other phenomena of coloured light. A powerpoint presentation accompanying this demonstration can be found in the presentation section. I have included some remarks on timing of the presentation but of course everything on this website is merely a brief suggestion to get your imagination started. If you have any questions with respect to the demonstration, theory or any other general aspects of optics please do not hesitate to email me at hseetzen@physics.ubc.ca Enjoy, Helge Seetzen