Color vision problems are more common than people think. Approximately 8 to 9% of men and 1% of women suffer from it. That Almost every 20 users of an HMI has color vision deficiency! In occupations dominated by men, this rate may be even higher.
Monochromaticity, i.e. color is not recognized at all, is rare. More common is a poor debility of sight for certain colors or combination of colors, such as the red-green or blue-yellow problems, or red or green blindness.
As an HMI designer, you have to adjust to color vision defects. The following websites may help: