Final answer:
Standard NATO markers with a blue background and red lettering are used to denote friendly NATO forces on military maps. The blue color represents NATO members, ensuring consistency in multinational operations.
Step-by-step explanation:
The question refers to the symbolism used in NATO markers. Standard NATO markers with a blue background and red lettering are used to denote friendly units and headquarters on military maps, indicating those are NATO forces. This identification system is part of NATO's standardized military symbology, which is used by member countries to ensure consistency and avoid confusion during multinational operations. The blue color represents NATO, as seen on maps like the Cold War Europe military alliances map, where NATO members are similarly colored in blue. The presence of red lettering on these markers isn't standardized; typically, the symbols and icons used are in black to contrast with the blue background for better readability.