Because Navy signal flags interest me so much I have been doing some research. I am going to do a series of posts on some of my findings. To learn more I suggest that you check out the link below as it has a wealth of information about the Navy and signal flags.
Below is text from the Navy Department Library.
The use of signals at sea, including flags, is first mentioned in
Greek mythology and confirmed in the ancient writings of Virgil and
Polybius. Prior to the development of radio, visual signals were
essential for communication at sea, and despite advances in
technology, remain important today. The use of flag signals by the
Royal Navy is documented as early as 1530, and evolved into an
unwieldy system later simplified by Admiral Lord Howe and others in
the late 1700s.
One of the first true flags was the vexillum carried by Roman cavalry. It was a square piece of fringed cloth hung on a crossbar at the end of a spear. Such a banner could serve as a rallying point for men in battle. Europeans carried their flags in this manner until the Middle Ages. I find it amazing that the use of signal flags started so far back. The more that I research the more interesting it is.
Many signals are accepted worldwide as calls for help. They have saved the lives of countless sailors and fliers in distress. The most familiar of these signals is the SOS signal of the International Morse Code. A similar signal is the flag hoist N C in the International Signal Code. They are colorful so that they can be seen from a long distance.
‘Dressing Ship’ is done with the International Code Signal Flags. Officer’s flags, club burgees and national flags are not used. The ship is dressed at 0800 and remains dressed until evening colours (an anchor only, except for a vessel’s maiden or final voyage).
The Yacht Ensign is hoisted at the stern staff and the Union Jack may be displayed at the bow staff. A rainbow of International Code flags are then arranged from the waterline forward to the waterline aft. Flags and pennants are bent on alternatively. It is good practice to follow a sequence of two flags, one pennant, two flags, one pennant etc.
The sequence of flags can be any order but as seen in the picture below it is recommended to vary the flags to give a harmonious colour pattern.
Here is a picture of a ship fully dressed.