Semaphore flag are usually red and
yellow for signalling between ships at sea and blue and
white for signalling to and from land
When you see the
Numerical flag it means that everything after
is a number. When the letter J (Alphabetic) flag is shown
in the number, it means that the number is finished and
the next sequence is alphabetic.
I am in
More details on the International Maritime
Signal Flags can be found here.