Color illusions are visual phenomena where the perception of color differs from the actual color of an object. These illusions occur due to the way our brains interpret light and color information, often influenced by surrounding colors, lighting conditions, and context. For example, the checker shadow illusion shows how a shadow can make two squares appear different in color, even though they are the same. These illusions highlight the complexities of human vision and how our brains process visual information. They can be used in art and design to create striking effects or to study the mechanisms of color perception in psychology.