It is a form of communication that was widely spread in Rome. It's also used as a semaphore symbol code in the Navy. One more interesting fact about flags is their designing. 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.