Unusual findings during an autopsy may come from peculiarities in the position, shape, size, weight, consistency, smell or color of organs. The following study was triggered by an autopsy case in which an unusual blue-green discoloration of organs, which changed during the autopsy, was noticed. A review of the local autopsy database, selected cases including the antemortem clinical documentation and the literature has been performed to clarify the etiology of these conspicuous discolorations and to evaluate their diagnostic value. The study showed that certain xenobiotics may lead to such discoloration. After systemic administration of methylene blue, darkening blue-green discoloration of organs, especially the brain and heart, can be observed. In addition, the systemic administration of toluidine blue also appears to be capable of causing such discoloration. Beyond that, drugs (like Rohypnol®) or other foreign substances (like detergents) containing warning colors, i.e. indigocarmin (E132) or Brilliant Blue FCF (E133) may cause discolorations of the upper gastrointestinal tract or the urinary bladder respectively. A blue-green, possibly darkening discoloration of organs during autopsy may point towards an antemortem administration of certain xenobiotics. The affected organs give an indication of the possible route of application and the type of substance. A differentiated interpretation of the etiology of such conspicuous discolorations at autopsy should only be made considering the (medical) history and, if necessary, complementary (toxicological) examinations.