The pop is an acoustic (sound wave) caused by the rapid expansion of gases produced by the reaction. The key element is the rapid release of energy due to the chemical reaction. This sets up a blast wave and thats what hurts your ears!! The colors have to do with tiny amounts of certain compounds that when heated by the blast gives the flame specific colors. An example of this is easy to do at home. Put some salt NaCl into a nice blue flame on the stove...the light will become very YELLOW. Thats because the heat causes electrons in sodium to jump up and down into different energy levels and when the electrons jump they emit characteristic radiation (light) of a specific wavelength (color)

The noise is created the explosions of the fireworks. The colors are properties of different elements, mostly metals that radiate at specific frequencies (colors) when excited. Sodium is yellow, and the bright pink color is titanium. I do not know the others, but a general chemistry book would have them.