Part I. The Chief Facts of Normal Colour Vision: 1. The bases of colour vision; 2. The spectrum as seen by the light-adapted (photopic) eye; 3. The spectrum as seen by the dark-adapted (scotopic) eye; 4. Regional effects; 5. Temporal effects; 6. Areal effects; 7. The evolution of colour vision; Part II. The Chief Facts of Colour Blindness: 1. Introduction: colour names; 2. Dichromatic vision; 3. Anomalous trichromatic vision; 4. Monochromatic vision; Part III. The Chief Theories of Colour Vision: 1. General review; 2. The duplicity theory; 3. The three-components theory (Young–Helmholtz); 4. The opponent colours theory (Hering); 5. Other theories; Index of subjects; Index of authors.