United States color - coded war plans During the 1920s and 1930s , the United States military Joint Army and Navy Board developed a number of color - coded war plans to outline potential U . S . strategies for a variety of hypothetical war scenarios . The plans , developed by the Joint Planning Committee ( which later became the Joint Chiefs of Staff ) , were officially withdrawn in 1939 in favor of five Rainbow Plans developed to meet the threat of a two - ocean war against multiple enemies . Colors . The use of colors for U . S . war planning originated from the desire for the Army and Navy to use the same symbols for their plans . At the end of 1904 , the Joint Board adopted a system of colors , symbols , and abbreviated names to represent countries . Many war plans became known by the color of the country to which they were related , a convention that lasted through World War II . As the convention of using colors took root , some were eventually reused , such as Grey , which originally referred to Italy but eventually became a plan for the capture and occupation of the Azores . In all the plans the U . S . referred to itself as " Blue " . The plan that received the most consideration was War Plan Orange , a series of contingency plans for fighting a war with Japan alone , outlined unofficially in 1919 and officially in 1924 . Orange formed some of the basis for the actual campaign against Japan in World War II and included the huge economic blockade from mainland China and the plans for interning the Japanese - American population of Hawaii . War Plan Red was a plan for war against Britain and Canada . British territories had war plans of different shades of red — the UK was " Red " , Canada " Crimson " , India " Ruby " , Australia " Scarlet " and New Zealand " Garnet " . Ireland , at the time a free state within the British Empire , was named " Emerald " . The plan was kept updated as late as the 1930s and caused a stir in American – Canadian relations when declassified in 1974 . War Plan Black was a plan for war with Germany . The best - known version of Black was conceived as a contingency plan during World War I in case France fell and the Germans attempted to seize French possessions in the Caribbean or launch an attack on the eastern seaboard . Considerations . Many of the war plans were extremely unlikely given the state of international relations in the 1920s , and were entirely in keeping with the military planning of other nation - states . Often , junior military officers were given the task of updating each plan to keep them trained and busy ( especially in the case of War Plan Crimson , the invasion of Canada ) . Some of the war plan colors were revised over time , possibly resulting in confusion . Interestingly , although the US had fought its most recent war against Germany and would fight another within twenty years , intense domestic pressure emerged for the Army to halt when it became known that the Army was constructing a plan for a war with Germany ; isolationists opposed any consideration of involvement in a future European conflict . This may have encouraged the Army to focus on more speculative scenarios for planning exercises . The Americas . War Plan Green . During the 1910s , relations between Mexico and the United States were often volatile . In 1912 , U . S . President William Howard Taft considered sending an expeditionary force to protect foreign - owned property from damage during the Mexican Revolution . Thus War Plan Green was developed . In 1916 , U . S . troops under General John Pershing invaded Mexico in search of Pancho Villa , whose army had attacked Columbus , New Mexico ; earlier , American naval forces had bombarded and seized the Mexican port of Veracruz , and forced Victoriano Huerta to resign the residence . In 1917 , British intelligence intercepted a telegram from the German foreign ministry to its embassy in Mexico City offering an alliance against the United States and assistance in the Mexican reconquest of the Southwest . Released to American newspapers , the Zimmermann Telegram helped turn American opinion against Germany and further poisoned the atmosphere between the USA and Mexico . Relations with Mexico remained tense into the 1920s and 1930s . Beyond Mexico . Additionally , between the United States Civil War and World War I , the American military frequently intervened in the affairs of Latin American countries , including Colombia / Panama , Haiti , Cuba , and Nicaragua . This policy continued during the 1920s and 1930s , and parts of " Gray " and " Purple " , although never officially activated , were used . Multilateral war plans . Some plans were expanded to include war against a coalition of hostile powers . The most detailed was Red - Orange , based on a two - front war against the Anglo - Japanese Alliance , which expired in 1924 . This was the contingency which most worried U . S . war planners , since it entailed a two - ocean war against major naval powers . Theories developed in wargaming Red - Orange were useful during World War II , when the United States engaged the Axis in both the Atlantic and Pacific simultaneously . Rainbow plans . Japan had used the opportunity afforded by World War I to establish itself as a major power and a strategic rival in the Pacific Ocean . Following World War I , most American officials and planners considered a war with Japan to be highly likely . It was reverted when the civilian government temporarily halted the program of military expansion , which was not to resume until 1931 . War Plan Orange was the longest and most - detailed of the colored plans . However , following the events in Europe in 1938 and 1939 ( the Anschluss , Munich Agreement , German occupation of Czechoslovakia , and Molotov – Ribbentrop Pact ) , American war planners realized that the United States faced the possibility of war on multiple fronts against a coalition of enemies . To that end , the Joint Planning Board developed a new series of war plans , the " Rainbow " plans - the term being a play on the multiple " color " plans that had been drawn up previously . The assumptions and plans for Rainbow 5 were discussed extensively in the Plan Dog memo , which concluded ultimately that the United States would adhere to a Europe first strategy in World War II . List of Color Plans . According to the public intelligence site , Global Security , the following plans are known to have existed :