Red-green colour blindness is a hereditary disorder of colour vision in which an individual has difficulty distinguishing between red and green colours. It is one of the most common inherited visual defects and is caused by mutations in the genes responsible for producing red or green cone pigments in the retina. These genes are located on the X chromosome; therefore, the condition follows an X-linked recessive pattern of inheritance. Males are more frequently affected because they possess only one X chromosome, whereas females usually become carriers unless both X chromosomes carry the defective gene. The two major forms are protanopia, involving the absence of red-sensitive cones, and deuteranopia, involving the absence of green-sensitive cones. Affected individuals generally have normal visual acuity but face difficulties in occupations requiring accurate colour discrimination, such as electrical work, aviation, and transport services. Diagnosis is commonly carried out using Ishihara colour vision charts. Although no permanent cure exists, adaptive strategies and specially designed lenses may help affected individuals manage daily activities. Anthropological genetics studies the distribution of colour blindness among different populations to understand patterns of inheritance, migration, and evolutionary significance. Balanced polymorphism