Color change refers to how glass will temporarily change color and will return to a base color when cleaned or ambient lighting is changed. Fuming refers to the process of superheating precious metals like Gold or Silver until they phase shift from a solid to a gas (at the atomic level), becoming an airborne gas that adheres the microsecond it comes into contact with the glass. After fuming, the particulate from use builds up on the inside, reflecting light back out through the fume layer where it is partially absorbed and partially refracted by the atomic layer of precious metals to give the appearance of a change in color.