There are two vague standards in the ADA — they are the finish standards, for both the sign backgrounds and the graphics, and they deal with glare or reflection, and contrast.
In the ANSI’s last revision cycle of the standards, a glare standard was established: use engraving materials with a gloss finish of 19 or less. Contrast is more controversial, but it’s important to remember that we aren’t talking about colors, but about darkness and lightness, which are measured in LRVs or Light Reflectance Values. If you choose a lighter color with an LRV of 50 or more, and then apply a formula that results in a contrast of 70 percent or more (.70) when you measure your darker color, your sign will be readable by the majority of people who can read a newspaper headline or recognize a friend’s face from about three feet. Just subtract the lower LRV number from the higher one, and then divide the answer by the higher LRV to get a decimal answer. Paint and plastic manufacturers should be able to tell you the LRV of the materials you purchase for signs.
We emphasize contrast and glare because even if you get some small detail wrong in the tactile graphics, if your signs have the contrast and glare standards licked, you will have met the needs of the greatest number of people with disabilities.
—Sharon Toji, The ADA Sign Lady