If you imagine four as four points, you can show it as a square. And this is how the ancient Greeks saw it, as a figure with four sides and four corners.
The four is an even number. Can be divided into two equal parts. For the ancient greeks, justice was a two-sided problem equal. So that, they used four, with its two equal parts, As the symbol of justice.
Was widespread belief in ancient times that the world was flat in shape, and spoke of the "four corners" of the Earth. And four is the number of the cardinal points: North, On, East and West. The color is the green and belongs to the sign of Cancer, The crab.
For many ancient peoples, the three was a magic number. It corresponded to the three parts of life: start, half and finally. It also corresponded to the three "kingdoms" of the Earth.: animal, vegetable and mineral. And wizards and witches generally worked in groups of three when they cast their magic spells.