At first glance, it seems difficult to associate harmony and impurity. But this notion takes on its real meaning with color diamonds, where the most important element is color. The presence of certain impurities can be tolerated under certain conditions, the main ones being that they do not interfere with the play of color or with the sparkle of the stone, and that they not be visible to the naked eye. For example, a light-colored impurity in a dark stone, or a dark impurity in a light-colored stone will be equally visible.