This is when a person has a difficult time with color vision. Cones are the light receptors in our eyes that detect color and there are three types: red, green, and blue detectors. If any of these color-sensors are abnormal, color-detection will become flawed and a person may be considered “color blind.” Many of the genes that control the development of these color cone cells are located on the X-chromosome. Males, who have only one X-chromosome to rely on, are more likely to have developmental color problems. In fact, about 8% of men have some color issues (usually difficulty with subtle red-green hues) while only 0.4% of women have this problem. There are a few conditions that can affect color as well, such as an active bout of optic neuritis and long-term use of the arthritis medication Plaquenil (though this is rare).