The document discusses the basic principles of colorimetry and the CIE (Commission Internationale de l'Eclairage) system for color specification. It explains that describing colors with words can be imprecise, as color perception varies between individuals. The CIE system aims to numerically specify colors based on the amounts of three primary light sources needed to match a color, rather than describe colors. Using mixtures of three carefully chosen colored lights as primaries allows the reproduction of a wide gamut of colors through adjustable combinations.