Never. A person can never have 2 hearts. Even if a person had, he would never survive.
In terms of biology, the red colored blood is oxygenated blood while the blueish colour of blood represents the deoxygenated blood. Specifically, all blood is red only, but in order to understand, scientists claimed that oxygenated blood is reddish while deoxygenated blood is blue.
Anyways, both are separated in heart due to the presence of septum. By chance, If a person had two hearts, then there would be no septum.
If there is no septum, the oxygenated and deoxygenated blood will mix together and will become poisonous. It will, unfortunately, lead to the death of the patient.
By Benjemin ☺️