Visual perception of architecture and town-planning is achieved by light and colour. On the other hand - light and colour are a vital formal medium in architectonical and townplanning design. What is more, light and colour can create the specific atmosphere and climate of the place (genius loci) in design, indicate the purpose of the place, its character or style. The article presents the elements of colour theory, problems of colouristic compositions and practical use. Such problems as: colour perception, emotional influence, symbols of colours and colour contrasts have been elaborated in the article. A supplement to the article is rich in illustration with commentaries.