What exactly does being colorblind prohibit me from?

Tough question: As an optometrist I have helped color blind students regain red-green discrimination using a x chrome lens. It depends on degree, type, and severity of color blindness which may require specialized tests.

Certain occupations: With color deficiency, you would have difficulty as an agricultural produce grader, painting, working in a store where color is important like cosmetics or fashion and certain occupations in law enforcement. Also color is important for pathologists although I am aware of some color deficient pathologists.