Soft-proofing for color blindness
CUD helps ensure that graphical information is conveyed accurately to people with various types of color vision impairment, including people with color blindness. Several countries have guidelines that require CUD-compliant graphics in public spaces.
The most common types of color blindness are protanopia (blindness to red) and deuteranopia (blindness to green). About one-third of color blind people are completely blind to red or green; most of the remainder have milder forms of color blindness.
In the figure below, the color wheel labeled A is the original image. The color wheel labeled B is a proof of how an individual with protanopia sees the original. The color wheel labeled C indicates a color combination that is perceivable to the greatest number of individuals.