What is the cause of root discoloration due to trauma?

After dental trauma, blood vessels in the pulp can rupture, allowing RED BLOOD CELLS to enter the dentinal tubules. The breakdown of RBCs releases HEMOGLOBIN, which breaks down further into HEMOSIDERIN and other iron-containing pigments that cause the characteristic GRAY/PINK/DARK discoloration of the tooth crown. This is similar to how bruises change color. White blood cell breakdown (B) doesn't cause this pigmentation. Endotoxins (C) cause inflammation, not discoloration. A is correct.