Most people believe they have good vision. Sure, you may need glasses for distance or reading, but overall people will say their vision is standard.
However, a lot of people have problems seeing colors and don't even realize it. 1 in 12 men are color blind, and 1 in 200 women have the same issue.
Color differential is a common way to tell if you may be color blind. Take this test and see if you can identify the hidden letters and numbers in the images!