How can color blindness affect the way an individual looks at a color blind test?

Color confusion: The tests are designed usually with dots of color along the axis which a color deficient person might confuse them. So by lacking the ability to pick out certain colors, the number or figure will not stand out from the background of dots and so will not be recognized. Some tests are sophisticated enough to indicate which type of color blindness is present.

Loss of color vision: In the retina of your eye, there are rods (for seeing in the dark) and cones (for seeing color and fine detail). There are three types of cones, similar to the three primary colors, and the color blindness test checks subtle differences between shades to see if you are missing cones of one of the color types (usually red or green). But usually you are not aware of any problem seeing things.