Colour Range The range of 40 colours are chosen according to mass tone (colour from tube), undertone (bias of colour when in a thin film), colour strength, relative opacity and the character of the pigment itself. The resultant colour spectrum ensures the largest number of colours can be mixed. The Cotman Water Colour range has a more uniform consistency than the Artists' Water Colour range and this benefits beginners as there is less to learn about each individual pigment. The Cotman Water Colour range also relates to the Winsor & Newton Artists' Water Colour range, e.g. Burnt Sienna in both ranges has the same hue. This enables artists to use colours from both ranges with minimal adjustment to their technique.