That perennial blue stain simply means that it's working. Reminds me of Hunter S. Thompson's Curse of Lono, where Ackerman retrieves his stash from an airline toilet and his arm remains blue, all through the remaining novel.
"There is only one way to get your arm dyed blue on a 747 flying at 38,000 feet over the Pacific. But the truth is so rare and unlikely that not even the most frequent air travelers have ever had to confront it -- and it is usually not a thing that the few who understand want to talk about.
"The powerful disinfectant that most airlines use in their toilet-flushing facilities is a chemical compound known as Dejerm, which is colored a very vivid blue. The only other time I ever saw a man come out of an airplane bathroom with a blue arm was on a long flight from London to Zaire, en route to the Ali-Foreman fight. A British news correspondent from Reuters had gone into the bathroom and somehow managed to drop his only key to the Reuters telex machine in Kinshasa down the aluminum bowl. He emerged about 30 minutes later, and he had a whole row to himself the rest of the way to Zaire."
