Quarantine "yellow jack" but this was also a name for yellow fever, which probably derives its common name from the flag, not the color of the victims (cholera ships also used a yellow flag). The plain yellow flag ("Quebec" or Q in international maritime signal flags) probably derives its letter symbol for its initial use in "quarantine", but this flag in modern times indicates the opposite—a ship that declares itself free of quarantinable disease, and requests boarding and routine port inspection. Australia has perhaps the world's strictest quarantine standards. Quarantine in northern Australia is important because of its proximity to South-east
Flag of Thailand In 1916 the flag was changed to show a white elephant in royal regalia. In 1917, the current design, but with the middle colour being the same red as the outer stripe, was defined as the civil ensign. The story goes that during a flood King Vajiravudh (Rama VI) saw the flag hanging upside-down, and to prevent this from happening again created a new flag which was symmetrical. Later in 1917, the middle colour was changed to dark blue, which was similar in tone to indigo, which at the time was regarded as the auspicious colour for Saturday, the day