Flag of Gibraltar

• The white color symbolizes peace and honesty;
• the red color symbolizes the revolutionary spirit, courage, strength, valor and endurance shown in the struggle for independence; 
• the castle symbolizes Gibraltar as a fortress; 
• the key represents the strategic position of Gibraltar at the gateway to the Mediterranean Sea. 

Most people mistakenly believe that the castle is Moorish. The castle on the flag represents Castile. The flag of Castile La Mancha was red and white with a golden castle on the red sector. This is the flag of Queen Isabella. She simply flipped the flag over so that the white was on top and the red was on the bottom. Then she placed her castle on the red spot, and the golden key hung on the castle gate. This key is the only thing that relates to Gibraltar, as it used to be considered the key to Spain, as well as to the Atlantic and Mediterranean seas.

In 1869, a letter was sent to all British colonies asking them to send the Colonial Office an image of a coat of arms or badge to be used by the governors for the Union Jack center.  At least eleven designs were to be submitted. On September 28, 1926, the late Sir Charles Monroe, Governor of Gibraltar, proposed that the coat of arms provided by Fernando and Isabella should rightfully be the true, correct and ancient coat of arms of Gibraltar, and that the motto "Montis Insignia Calpe", which literally means "The Mountain named Calpe", should also be part of the coat of arms. This could be done without a royal warrant, but only if a certified and accurate copy of the Spanish grant of Fernando and Isabella from 1502 was obtained.  After receiving such a copy, the coat of arms was approved.