For who does not know: there is a single push button for 4 colors. It works with a gravity pendulum system: To select a color, just hold the pen horizontally (or very much inclined), to make it turn on itself so as to have the icon of the visible color desired (c ' is to say top) and press the button. tadaaa ...
Only complaint mechanics is not as snug as other multifunction equipped with the same system. (Sometimes this is not the right color comes out)