Green blindness, also known as second color blindness, is a condition in which the patient cannot distinguish between light green and dark red, purple and cyan blue, or fuchsia and gray, and sees green as gray or dark black. A child in an art training class who drew very well always painted the sun green and the canopy of trees and grass brown, but it turned out that he was green color blind. The clinical term for red and green color blindness is red-green color blindness, which is more common in patients. When we talk about color blindness, we usually mean red-green color blindness. It is a congenital color vision disorder in which the two colors, red and green, cannot be distinguished. The gene controlling red-green colorblindness is located on the X chromosome and is recessive, usually denoted by Xb. The Y chromosome is too short and lacks the corresponding homologous segment with the X chromosome and does not have the gene controlling colorblindness. Color blindness is mostly due to congenital inheritance and, in a few cases, to disorders of the visual pathway transmission system. It is usually transmitted in females and manifested in males. Statistically, the prevalence of color blindness is 5% in males compared to 1% in females. People with congenital color vision disorders are often unaware of their abnormal color discrimination and are mostly detected by others or during physical examinations. All workers in transportation, art, chemistry, medicine, etc. must have normal color vision, so color vision screening has become a routine item in military service, employment, and pre-school medical examinations.