What is the origin of the term "red team" for a group simulating an adversary?

In information security, the military, etc., a "red team" is a group that plays the role of an adversary in a simulated engagement (with the "blue team" on the other side of the engagement).

What is the origin of this term? I've seen it suggested in various places that it could have origins in the Cold War–era US Military, as a reference to the red color of the Soviets, for a group playing the role of Soviets in a military or intelligence exercise. However, I couldn't find any authoritative reference.

Is this origin story accurate? What is the origin of this term (ideally with sources)?

Solution 1:

Further to Stuart F's comment:

The war college tradition of modern war games began with the von Reisswitz's Kriegsspiel in the early 19th century. As it developed through many variants over the course of the 19th century, the Kriegsspiel established conventions of war gaming, such as identifying the opponents as red and blue, the use of maps and umpires, and fundamental rules for movement and combat resolution. H. Schramm et al.; Collection, Laboratory, Theater: (2005)

In 1811, Two young Prussian Princes, Fredrick and William, learnt of a wargame invented by Herr von Reisswitz who was living in Berlin. They were in [sic] intrigued by the idea and soon Reisswitz was given a room in the palace to build a large plaster contoured model of countryside at the arbitrary scale of 26 inches to the mile. The troops were represented by wooden blocks with coloured paper stuck on them. The games were regulated by a set of rules to decide the crucial matters such as movement and firing. Withing a year, the king himself started to play the wargame.

The development of the game was then led by Von Reisswitz's son, who turned the rules for the game into something resembling a simulation of war. The playing area model was replaced with more practical maps at a scale of 8 inches to 1 mile. Dice were introduced to represent the element of chance in war. The two sides were labelled as 'red' and 'blue'; a naming convention that is still in wargaming.

In 1824, Reisswitz gave a lecture on the game to the general staff, followed by a demonstration. The Prussian Chief of Staff, General Muffling, received the game somewhat coldly at first, 'but as the operations expanded on the map, and move by move the combatants worked out their plans, the old general's face lit up, and at last he broke out with enthusiasm: 'It's not a game at all, it's training for war. I shall recommend it enthusiastically to the whole army'.

Professionally [sic] wargaming was then established.

John Curry; Verdy's Free Kriegspiel (2008)

As to why red and blue were chosen, they might be a carryover from Roman games.

Chariot racing was very popular in ancient Rome, where races were held between teams (or factiones). The four Roman racing teams were known by their colors—red, white, blue, and green. Red and blue teams can be seen in this 19th-century illustration of a race at the Circus Maximus. DK; Pocket Genius Horses: facts at Your Fingertips (2016)

Yet Roman chariot racing came as close as anything in the ancient world to the team sports we know today. Each chariot belong to one of four "factions" or colors, called Blue, Green, Red, and White. Tombstones and other monuments for charioteers always indicated what color they belonged to when they won their victories. Spectators were loyal to their colors, and might identify themselves as Blues or Greens depending on what team they rooted for. Anne Mahoney; Roman Sports and Spectacles (2001)

Tertullian claims that there were originally just two factions, White and Red, sacred to winter and summer respectively. By his time, there were four factions; the Reds were dedicated to Mars, the Whites to the Zephyrs, the Greens to Mother Earth or spring, and the Blues to the sky and sea or autumn. Each faction could enter a team of up to three chariots per race. Members of the same team often collaborated against the other teams, for example to force them to crash into the spina (a legal and encouraged tactic). The driver's clothing was color-coded in accordance with his faction, which would help distant spectators to keep track of the race's progress. "Chariot Racing", Wikipedia