Winsor & Newton tubes have labels that let you know what is in the colour and will indicate whether or not you are using a single pigment colour or a mixture. Single pigment colours are often the preferred choice for artists so that mixtures remain clean. Sometimes mixtures are necessary to achieve a colour if it is no longer produced or is too toxic to be safe by modern standards. It is also useful for certain colours where a consistent colour bias is desired. Cadmium Orange, for example, is an example of a perfect formulation from two pigments to achieve the perfect formulation between red and yellow bias. There may also be gaps in a range of original pigments, such as with green; in this case, formulations allow for a wider variety of permanent greens to broaden your palette.