A twisted liquid crystal device includes a liquid crystal layer and first and second alignment layers disposed in opposite sides of the liquid crystal layer. The first and second alignment layers have respective alignment directions which are mutually inclined. A first linear polarizer is disposed on the opposite side of the first alignment layer to the liquid crystal layer. Electrodes apply a variable voltage across the liquid crystal layer which has a twisted liquid crystal structure and is arranged for operation in a surface switching mode with first and second regions of the liquid crystal layer adjacent the alignment layers being mutually optically de-coupled so as to act, within the liquid crystal layer, when in use, like a pair of separate, active optical retarders having mutually inclined optic axes and optical retardations which can be varied within a range to cause color.