For example, normal color vision is vital in such jobs as color printing and color photography. Abnormal color vision can even be dangerous in certain situations, such as in rail and water navigation. For this reason, persons with color vision defects are excluded by law from certain occupations. Color vision depends on the absorption of light by visual pigments contained within specialized cells in the eye called photoreceptors. Rods , which provide vision in dim light, have no ability to distinguish between colors.
Cones are responsible for color vision.
There are three different types of come pigment in the normal eye. Color vision occurs within the visual part of the brain compares electrical signals from the different types of cones. Defects in color vision are either inherited or acquired. Inherited defects result mainly from missing or incorrect visual pigments. There are different types of inherited defects, with different levels of severity.