The embedded colour you see inside the cd is a layer of dye, not the metal foil found in commercial cd's. In home cd burning, the laser changes the colour of the dye slightly. That's what's detected when the cd is read. In a commercial cd the laser actually burns a small pit in the metal foil. This is much more permanent and not susceptible to sunlight or heat deterioration. Too hard to do with home kit, though. note: These pits are so small that bacterial contamination can be a major problem.