The rules of Heraldry still determine the way flags look. The symbolic associations with the colors of flags deal with ancient Heraldic traditions. If you ask about the colors of the flags of the world, the dominant ones are white, blue, red, green, yellow and black. When it goes about symbols that are depicted in flags of different countries, there is a great variety of them. It can be the images of sun, stars, crosses, triangles, squares, animals and even the writings, like on the one of Saudi Arabia. It would be interesting for you to know that one of the biggest flags in the world is the Greek one.