Final answer:
Cyanosis is not manifested until the saturation of oxygen is less than 90%
Step-by-step explanation:
The saturation of oxygen needs to be less than 90% for cyanosis to be manifested. Cyanosis is the bluish discoloration of the skin and mucous membranes due to low levels of oxygen in the blood. When the saturation of oxygen drops below a certain level, it indicates that there is not enough oxygen being delivered to the tissues, leading to cyanosis.