Color blindness is usually genetic, but can also be caused by traumatic injury or exposure to chemicals. There are three types of color blindness – one type makes it difficult to distinguish between red and green, the second type makes it difficult to distinguish between blue and yellow, and a third type is actually complete color blindness in which the eye cannot detect any colors at all. Red-green color blindness affects 10% of males in the United States, while only 0.5% of women are affected, and 99% of all people with color blindness have red-green color blindness.