Fire is a chemical reaction that releases energy as heat, which vaporizes the fuel's chemicals, forming a flame composed of energetic molecules. The flame's color arises from excited electrons transitioning to stable orbitals, influenced by the specific chemicals in the fuel. Higher temperatures result in different flame colors due to increased energy output. Additionally, the color of coals is determined by black body radiation, correlating with the fire's temperature. Understanding these concepts clarifies the nature and appearance of fire.