Color vision deficiency (formerly known as color blindness) is common as a congenital and as an acquired condition. Some professions, most famously commercial aviation, require their members to demonstrate normal color vision. In the USA and UK, no restriction is placed on the ability of the color-deficient doctor to practice medicine, though there is evidence that certain clinical discriminations are harder for such doctors. Generally ignored has been the difficulty, and the potential for error, that arises from the use of color codes in clinical equipment. In this review, we introduce the basic concepts of color deficiency, summarize evidence for the challenges it poses to the doctor, examine global variation in policy, show the potential for confusion among clinical color codes, and suggest how the current situation could be improved to enhance both patient safety and the wellbeing of the color-deficient doctor.