Source : WordNet®

colouring
     n 1: a digestible substance used to give color to food; "food
          color made from vegetable dyes" [syn: {coloring}, {food
          coloring}, {food colouring}, {food color}, {food colour}]
     2: a visual attribute of things that results from the light
        they emit or transmit or reflect; "a white color is made
        up of many different wavelengths of light" [syn: {color},
        {colour}, {coloring}] [ant: {colorlessness}]
     3: the act or process of changing the color of something [syn:
        {coloring}]