Original Medium Shade will deepen natural skin colour by 2 to 3 shades. The colour in the mousse is a guide to enable you to see where you are applying the tan. The active tanning ingredient, DHA, is colourless. Once you rinse the colour guide off in the shower your tan will continue to develop and your skin colour will gradually deepen over a period of a few hours. You can leave Cocoa Brown 1 HOUR TAN on overnight but it is not necessary as after 3 hours, the skin has absorbed the maximum amount of active ingredients.