A patient brought to the emergency room after a road traffic accident shows cyanosis. Which of the following is TRUE regarding in this patient?

Cyanosis becomes apparent when the concentration of reduced hemoglobin in capillary blood exceeds 40 g/L (4 g/dL). Cyanosis is an extremely late sign of hypoxemia and may not occur at all if there has been extensive blood loss. Indeed, a patient has to have 5 grams of deoxygenated hemoglobin per 100 cc of blood for cyanosis to occur. Ref: Loscalzo J. (2012). Chapter 35. Hypoxia and Cyanosis. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.