How can someone become color blind?

Mostly genetic: By far the most common cause of color deficiency is a lack of 1 of 3 types of cones in the retina. This is inherited on the x chromosome. Which means it's most often passed on to sons from mothers. The mother's dad usually has the condition. Less common causes are medication toxicity and conditions affecting the retina or optic nerve, like ms + retinitis pigmentosa.

Mostly inherited: The most common forms of color blindness are inherited. They are that way from birth. Less common is developmental such as advanced diabetic retinal disease which fades out color recognition. Retinal degeneration like retinitis pigmentosa lead to color blindness and there is a rare form of stroke which can cause cortical color blindness.