An empirical exponential equation is proposed to characterize the transfer functions of the image signals to tristimulus values of twist nematic (TN) liquid crystal displays (LCDs). Parameters of the empirical equation can be determined according to the colorimetric measurements of the test panel without knowing the panel's physical details. A two-stage forward model is also proposed to model the color characteristics of TN LCDs by using the empirical function. Moreover, a backward model is derived to reproduce desired colors accurately on TN LCDs. The main benefit of the study is that only 12 colors should by measured to characterize color rendering on TN LCDs.