Color change materials are substances that alter their color in response to changes in temperature, light, or other environmental factors. These materials can be found in various applications, such as in thermochromic inks used for mood rings or photochromic lenses that darken in sunlight. The science behind color change materials often involves special chemical compounds that undergo structural changes when exposed to specific stimuli. This property makes them useful in fields like packaging, where they can indicate temperature changes, or in smart textiles, which can change color for fashion or safety purposes.