Which colors do a color blind person have trouble distinguishing?

Color blindness, also known as color vision deficiency, affects a person's ability to perceive certain colors correctly. There are different types of color blindness, but the most common type is red-green color blindness. People with red-green color blindness have difficulty distinguishing between shades of red and green. For example, they may see red as brown or dark green, and green as brown or dark red.

Other types of color blindness include blue-yellow color blindness (in which people have difficulty distinguishing between shades of blue and yellow) and complete color blindness (in which people see only shades of gray). Complete color blindness is rare, affecting only about 1 in 100,000 people. Most people with color blindness are born with the condition, although it can also be caused by certain diseases or injuries.