What poison could be dissolved in an alcoholic drink or hot food that would leave a blue stain (that is not lividity) around the victim's mouth? I doubt it would be anything sophisticated, something that could be ordered online or purchased through the right kind of specialty shop. Wondering if a person I know has killed two people at two different times using poison. Once was perhaps with a gradual build-up / long series of doses, the other was probably a single very large dose.