Color blindness is a condition in which a person is unable to differentiate between colors. Color blindness is not a form of complete blindness instead it is a deficiency which doesn’t allow a person to see certain specific colors such as yellow and blue or red and green.
Dr Shinobu Ishihara from Japan introduced the most popularly known color blindness test in 1917. The test is a color perception test for red-green color deficiencies. It consists of a set of colored dotted plates (PseudoIsochromatic Plate or PIP), each of which shows certain numbers or patterns such as random lines.
Retina is the light-sensitive layer of tissue that surfaces the inside of your eye. Color blindness is caused by a difference in how the light-sensitive cells found in the retina of the eye respond to certain colors. These cells of the retina that enable color distinguishing are called cones.