Composite colloids were prepared via grafting optically responsive spiropyran polymer brushes onto silica colloids. Similar to spiropyran, the polymer brushes undergo a reversible inversion from a hydrophobic state to a hydrophilic state upon irradiation with UV light (or vice versa by visible light). The composite colloids can thus reversibly transfer between oil and water phases, and this can be remotely triggered using light. At intermediate stages of irradiation, both hydrophobic and hydrophilic components coexist, resulting in the amphiphilic performance of the composite colloids. Such amphiphilic composite colloids can be used as particulate emulsifiers.