What is the real meaning of color blind?
In the vast majority of cases, “color blind” refers to people who have a deficiency in their color vision. In fact, “color vision deficiency” is a more appropriate term. People with deficiencies generally confuse certain hues. For example most have some form of red-green confusion while others exhibit a yellow-blue confusion. There are very rare cases of people with monochromatic vision who can only see in shades of gray (they confuse all hues). There is more information in this answer.
