What about the nautical semaphore flags? Those are used for signalling and communications between ships, or at least they were, and if memory serves me correctly many of the flags are red, so that they stand out. I;m not sure if they are still in use but I believe they are.
There may be many red flags. But this one was hoisted on the 'virgin' voyage of the Queen Mary 2, at this point in time, when people are very concerned about terror attacks. It's a flag that just appeared in the news photos, on the world's largest cruiseship, flown by a queen named Mary. It was on another woman, the SOL, where a red flag also prominately waved. Turned out, it was just prior to 911.
Thus, I merely point out that Queen Mary 2 is/was waving a red flag. She's headed toward Florida. The Queen Mary thread details her opulance and glamour. Most passengers are from North America.