The green colour of a liver is not a stain

People think bilirubin turns tissue green, but that is wrong. Bilirubin is yellow. It is the oxidised form, biliverdin, that is green, and that happens in the liver’s cells, not just floating in the blood. When a liver is diseased and bile backs up, the yellow pigment accumulates, but the green you see in pathology slides is actually biliverdin sitting in the cells. It is a chemical shift, not a dirt mark. I looked into whether this green colour triggers an immune response, or if the tissue just sits there, stained. The answer is that the tissue is passive. The colour is a side effect of the chemistry, not a signal that sets off the inflammation. The inflammation comes from the damage to the cell structure itself. I can explain the colour change perfectly, but I cannot tell you exactly how fast the cells die once the bilirubin hits a certain threshold. That number is still slippery.