On the basis of the analysis of color characteristics of different LC display units the criterion for an assessment of an unchromaticity of black-and-white images is entered. For the adequate description of the optical properties of the LC modulator the necessary set of three characteristics is offered: contrast of the modulator, average on a range; the average on a range passage of the modulator for a status «is opened»; a modulator akhromatichnost is «open» for a status.