The color that we see around us are from objects that are either original sources (luminous objects) or secondary sources (illuminated objects). Luminous objects are things that emit light; candles, light bulbs, and stars are some examples. Illuminated objects, on the other hand, have color because they reflect light. How does something emit light? In order to answer this, we must go to the atomic level. Over the years, many different models of the atom have been developed by scientists to explain different things. To explain how light waves originate, Niel Bohr's model of the atom probably works the best. In this model, atoms are made up of protons and nutrons scrunched into the central nucleus, and electrons orbit this nucleus in set "orbits." Now, usually, an atom with low energy has all of its electrons in a low and stable energy level. These electrons are in their ground state, and stay in orbits that are close about the nucleus. When the atom receives energy from the surrounding (in the form of heat, electricity, etc...), its electrons are boosted into a higher energy level. They actually move to a new orbit that is farther away from the nucleus. Now, this situation, like all good things, doesn't last forever. The electrons eventually move back down to their ground state. In order to do so, they must release energy in the form of photons, which, of course, our eyes perceive as colored light. As stated before, the amount of energy in the released photon is the thing that determines its color. All of the different elements in this world give off different colors when their respective atoms are given energy. This is because each element has its own electron orbitals, and therefor, different amounts of energy that it gives off. In fact, scientists can determine the composition of stars simply by the colors of the light they give off.