How do we determine contrast on signs? What colors work best?
Contrast is between light and dark, not between colors. For instance, a very pale grey (almost white) would be fine with a charcoal grey background. Brown and green or red and black do not, however, contrast for people with defective color vision. And contrary to most people’s belief, signs with a red background, even with white characters, are actually among the most difficult to read. Although contrast is not defined in the guidelines, the Appendix does suggest a minimum of 70%. The formula given in the appendix works quite well if you use one color that is very light and one that is quite dark. The formula fails, however, when you use two dark colors; it will indicate a much higher contrast than the colors actually have. The scientific reasons are complex, but an ANSI Task Group is working on a better formula. Research into color has yielded many useful guidelines for designers. Early research sponsored by the Access Board shows, for instance, that a 70 percent contrast, using the f
