Jolly roger; a black flag with a skull, skull and swords, or just swords. This flag is flown by pirates.. It is an invitation to surrender, and an indication that those who surrender will be treated well.
Red Roger; a jolly roger with a red background. It has the same meaning as a Jolly Roger, except that no quarter will be given.
Yellow jack; a yellow flag, sometimes with a skull. This is flown to indicate a contagious illness.
Blue Split; A blue flag split with a yellow line. The ship carries an urgent message and requests communication.
Blue; A blue flag is a sign of peace and a wish to communicate.
Red Diamond: A white flag with a red diamond in the center means the ship is disabled and requests help.
White; a sign of surrender or peace.