There are two blank national flags, Libya's and Fujairah's. Libya's national flag is dark green, and has nothing else on it. It's representative of the county's devotion to Islam and the fact that green is its national color. Fujairah, part of the United Arab Emirates, is has a flag that's totally red, with no imagery present.
Railway signal flags are also among the blank flags of the world. Blank railway signal flags come in three colors: red, yellow and green. Green signal flags mean full speed for the incoming train, while yellow means to slow down, and red signal flags mean to stop.
RAS, or replenishment at sea, are signal flags used by the U.S. Navy to communicate to other ships at sea without using radio transmissions. There are six RAS signal flags, also called station markers, that are blank. RAS station marker #1, which is orange, means missiles are on board. RAS station marker #2, a green flag, means ammunition is on board. RAS station marker #3, a red flag, means fuel oil is on board. RAS station marker #4, which is blue, means diesel fuel is on board. RAS station marker #5, a yellow flag, means gas is on board. RAS station marker #6, which is white, means water is on board. Two other naval signal flags are blank, Quebec and Bravo. The yellow Quebec signal flag means the ship is requesting health clearance, while the blue Bravo signal flag means the ship is handling explosives.
The Canadian military also uses blank flags for communication purposes. In the Canadian military, blank flags are used in communicating between military convoys. A blue flag represents the lead vehicle in a convoy. The yellow flag means the vehicle is not able to proceed, probably for mechanical reasons. A green flag means the vehicle is the last in the convoy, and a red flag means the vehicle is carrying dangerous materials, either HAZMAT or fuel.
