Abstract: A method and apparatus are disclosed for using information about colors, fonts, and viewing distances to predict the legibility of a sign. The invention takes into account the colors used in the sign, in order to allow the use of many different color combinations while still avoiding "strobing" from simultaneous contrast caused by complementary afterimages. A computer program accepts information such as the desired visual acuity, viewer velocity (for signs viewed from a car), font specification, ambient light strength, and the desired typeface color and background color. The program then predicts the legibility of a sign which uses the fonts and colors indicated under the given conditions. Thus, the program may be used to assess the effect of various changes on the sign's legibility without actually rendering or building the sign, installing it, and looking at it.