Colour used imaginatively can add depth to a painting and aid recession, create mood and passion. Colours possess 4 basic qualities i) Hue ii) Value (light or dark) iii) Chroma or purity - free from any White constituent and iv) Temperature (warm or cool). The chemical and physical science of colour is extensive and beyond the remit of this glossary; however, do not be deterred and research if you so wish. Colour can be gradated or flat, local or atmospheric, light or dark. See complementary, secondary, tertiary colours.