The principle of custom color changing cups with lids lies in the use of special thermochromic materials. These materials are designed to respond to changes in temperature. When hot liquid is poured into the cup, the heat causes a chemical reaction within the thermochromic coating, resulting in a visible change of color. The color transformation occurs precisely due to the variation in temperature, allowing the cup to display different hues depending on the temperature of the contents. This unique feature adds an element of surprise and entertainment to the user's experience, making the custom color changing cups with lids a popular and interesting choice