A system, method and apparatus for detecting a faulty bulb within an ornamental light string. The light string includes a plug at one end, a receptacle at an opposing end and a plurality of lamps in series arrangement coupled therebetween using an electrical wire. Each lamp includes a bulb, a socket coupled to the bulb, and a light source within the bulb that is electrically coupled to the electrical wire. The bulb includes a translucent cover coupled to a holder. The holder is removably coupled to the socket. The socket comprises a temperature-dependent color changing material, which can be thermochromic ink, which allows the outer surface of the socket to change colors depending upon its temperature thereby assisting in identifying a faulty bulb requiring replacement.