A pair of polarizing plates are disposed on two sides of a TN-type liquid crystal cell constituted by a liquid crystal twist-aligned at a twist angle of 80.degree. to 120.degree.. A retardation plate is disposed between one of the polarizing plates and the liquid crystal cell in such a manner that the optical axis of the retardation plate crosses the transmission axis of the adjacent polarizing plate at 45.degree.. The pair of polarizing plates are arranged such that their transmission axes are parallel to each other. The liquid crystal cell is arranged such that the optical axis of the retardation plate crosses the aligning direction of the liquid crystal molecules on the substrate side adjacent to the retardation plate at 45.degree.. A liquid crystal driving circuit is connected to the liquid crystal. This circuit serves to change the voltage applied to the liquid crystal to change the polarized state of light transmitted through the liquid crystal so as to change the color of emerging light.