hese dyes are water-insoluble but soluble in alcohols, chlorinated hydrocarbons, or liquid ammonia. These colours are applied by dissolving in the target, which is invariably a lipid or non-polar solvent. The Colour Index uses this as a classification and naming system. Each dye is named according to the pattern: – solvent + base colour + number They are used for colouring synthetics, plastics, gasoline, oils and waxes.