History ColourCodedForYourConvenience / RealLife

** Red = Italy. Still used by Ferrari in UsefulNotes/FormulaOne.
** Light Blue = France
** Gray or silver = Germany, still used by Mercedes Benz and Audi. German racing cars are thus known among fans as "Silver Arrows".
** Dark Green = UK, usually called British Racing Green, used by Aston Martin in sportscar racing, and Caterham in F1.

*** Beginning in the 18th Century, White became associated with loyalist or monarchist factions during European civil wars, e. g. the white cockade of the Jacobites, and the white badges and flags used by Royalists during the French Revolution and by the "Whites" of the Russian Civil War. Hence, White becomes associated with the reigning monarch, and Red with the rebels seeking to overthrow that monarch[[labelnote:note]]However, this is in part coincidence, result of the Bourbon dynasty's long association with the colour white (going back to Henry IV's white plume) and the fact that Czarist armed forces had been using white flags with a blue saltire since the middle ages.[[/labelnote]].

* This is quite common for any metropolitan mass transit system that's extensive enough to have multiple lines. In older systems where the lines originally had names, it's a bit of a tossup whether people use the colors to refer to the lines: for instance, in [[UsefulNotes/PhiladelphiaSubways Philadelphia]], while the two main mass-transit routes are consistently colored (the Broad Street Subway is always colored orange, the Market-Frankford Elevated is always blue), even extending to the colors of the signage and the colors of the seats in the cars, Philadelphians almost invariably call them the "Subway" (or the "Sub") and the "El" rather than the Orange Line and Blue Line. On the other hand, in some places, the colors have successfully replaced the names in common speech; a Chicagoan who calls the [[UsefulNotes/ChicagoL Brown Line]] the "Ravenswood Branch" is definitely an old-timer. Finally, in some newer systems, the lines never had another name to begin with; the colors ''are'' the names. (The UsefulNotes/WashingtonMetro is a prime example, as it was built from scratch in the 1970s.)

* This is quite common for any metropolitan mass transit system that's extensive enough to have multiple lines. In older systems where the lines originally had names, it's a bit of a tossup whether people use the colors to refer to the lines: for instance, in [[UsefulNotes/PhiladelphiaSubways Philadelphia]], while the two main mass-transit routes are consistently colored (the Broad Street Subway is always colored orange, the Market-Frankford Elevated is always blue), even extending to the colors of the signage and the colors of the seats in the cars, Philadelphians almost invariably call them the "Subway" (or the "Sub") and the "El" rather than the Orange Line and Blue Line. On the other hand, in some places, the colors have successfully replaced the names in common speech; a Chicagoan who calls the [[UsefulNotes/ChicagoL Brown Line]] the "Ravenswood Branch" is definitely an old-timer. Finally, in some newer systems, the lines never had another name to begin with; the colors are the names. (The UsefulNotes/WashingtonMetro is a prime example, as it was built from scratch in the 1970s.)

* This is quite common for any metropolitan mass transit system that's extensive enough to have multiple lines. In older systems where the lines originally had names, it's a bit of a tossup whether people use the colors to refer to the lines: for instance in [[UsefulNotes/PhiladelphiaSubways Philadelphia]], while the two main mass-transit routes are consistently colored (the Broad Street Subway is always colored orange, the Market-Frankford Elevated is always blue), even extending to the colors of the signage and the colors of the seats in the cars, but Philadelphians almost invariably call them the "Subway" (or the "Sub") and the "El" rather than the Orange Line and Blue Line. On the other hand, in some places, the colors have successfully replaced the names in common speech; a Chicagoan who calls the [[UsefulNotes/ChicagoL Brown Line]] the "Ravenswood Branch" is definitely an old-timer. Finally, in some newer systems, the lines never had another name to begin with; the colors are the names. (The UsefulNotes/WashingtonMetro is a prime example, as it was built from scratch in the 1970s.)

* This is quite common for any metropolitan mass transit system that's extensive enough to have multiple lines, although it's a toss-up whether the residents of a particular city call the lines by their colors or their actual names (assuming they have other names; some just pick a colour and use that as the name).

*** Black Beret for all other Army personnel[[note]]Only in their Class-A Uniforms. For their battlefield fatigues, they wear camoflauge patrol caps.[[/note]]

* While no law in Mexico requires gas stations to use specific colors for their different fuels (as long as each particular gas station uses clearly labeled colors it's fine), chances are you'll see regular gasoline pumps colored green, high octane pumps colored red, and diesel pumps colored black. This is because these are the colors used in PEMEX fuel stations, which until 2018 held a state-controlled monopoly on fuel retail. These colors are well known enough that if you drive up to a gas station that doesn't use these colors (such as Shell, Akron or Total) and ask for "green" fuel, you'll be served unleaded gasoline.

* USB 3.0 ports are blue. USB 2.x and earlier are not.

** Red = Italy. still used by Ferrari in UsefulNotes/FormulaOne)

** Gray or silver = Germany, still used by Mercedes Benz and Audi.

** Blue = 20 Euro, $5 Canadian, $10 Australian, $10 New Zealand, $20 Mexican pesos, $500 Mexican pesos (new), ₽50 Russian, 5 Soviet/Imperial rubles; Brazil has dark blue for $100 and a lighter one for $2

** Blue = 20 Euro, $5 Canadian, $10 Australian, $10 New Zealand, $20 Mexican pesos, ₽50 Russian, 5 Soviet/Imperial rubles; Brazil has dark blue for $100 and a lighter one for $2

** Purple = 500 Euro, 20 Pounds, $10 Canadian, $50 New Zealand, ₽500 Russian, 25 Soviet/Imperial rubles, $5 Brazilian

** Blue = 20 Euro, $5 Canadian, $10 Australian, $10 New Zealand, ₽50 Russian, 5 Soviet/Imperial rubles; Brazil has dark blue for $100 and a lighter one for $2
** Brown = $100 Canadian, ₽100 Russian, $50 Brazilian (though nearly orange)
** Green = 100 Euro, 5 Pounds, $20 Canadian, $100 Australian, $20 New Zealand, ₽1000 Russian (though significantly bluish), 3 and 50 Soviet/Imperial rubles; Brazil used it for $1 before it was put out of circulation.

** Orange = 50 Euro, 10 Pounds, $5 New Zealand, ₽5000 Russian
** Pink = $5 Australian, 50 Pounds, $10 Brazilian

* The mechanical keyboard industry uses some common colors to denote switch types:

** National Guard[[note]]Unlike its US counterpart, Russian National Guard is under federal command and principally an intervention force against domestic unrest, closer in functions to Italian Carabinieri, French National Gendarmerie, or Chinese People's Armed Police [[/note]] (used to be the Internal Troops of the Ministry of Interior before the 2016 reform): Burgundy stripes

** National Guard[[note]]Unlike its US counterpart, Russian National Guard is federal and largely an intervention force against domestic unrest, closer in functions to Italian Carabinieri, French National Gendarmerie, or Chinese People's Armed Police [[/note]] (used to be the Internal Troops of the Ministry of Interior before the 2016 reform): Burgundy stripes

** Spetsnaz of the Ministry of Interior (MVD): Burgundy stripes

** Sailors: Black stripes
** Naval Infantry, including [[ElitesAreMoreGlamorous Naval Spetsnaz]]: Dary blue stripes

** Ministry of Interior (MVD): Red stripes

** Green = 100 Euro, 5 Pounds, $20 Canadian, $100 Australian, $20 New Zealand, ₽1000 Russian (though significantly bluish), 3 and 50 Soviet/Imperial rubles; Brazil used it for $1, before it was put out of circulation.

* Fruits change colour depending on how ripe they are. This is thought to be why humans evolved colour vision in the first place. Additionally, Women are less prone to colorblindness than men, and some women are able to see more shades of red than men are. They believe this is a holdover from the old caveman days, when women were the gatherers and had to differentiate between "safe to eat" red berries and "highly poisonous" red berries.

* Cigarette packaging ''tends'' to follow a general color-coding scheme, although it's far from universal. About the only thing that's consistent across most brands is that if it's in a green or predominently green pack, it's menthol.[[note]]And even that isn't universal; Canadian brand Export A doesn't even sell a menthol and uses green for its full-flavor pack.[[/note]]

*** Even ''cheese'' is color-coded in New Zealand - cheddar ("tasty") cheese is red, colby is yellow, edam is blue, mild cheese is light green, and mozarella is dark green.

* If you take a look at your local hardware store in the powertools section, you'll likely notice a whole rainbow of colours, usually associated with their own brand:

* At US self-serve gas stations, pump handles for diesel fuel are usually colored green to distinguish them from regular unleaded gasoline. This is ''very'' important, as mistakenly putting diesel in an non-diesel car will ruin your whole day. And most likely your whole car.

** Purple: Advent[[note]]Late November until Midnight, December 24/25[[/note]] and Lent [[note]] Ash Wednesday until the Wednesday of Holy Week[[/note]], as a sign of penance (though some have tried to differentiate between two different shades for the two seasons, the Church just says purple is the color). Priests also wear purple stoles while hearing Confession or administering last rites. Purple is also often worn for funeral Masses, as well as for masses with annointing of the sick.

** For examples that aren't in the flag: the Netherlands are orange after the royal family (the House of Orange), Italy blue for its former royal family (House of Savoy), Germany use the Prussian white harkening from imperial days (the House of Hohenzollern), Australia use [[https://en.wikipedia.org/wiki/National_colours_of_Australia green and yellow after a local plant]], New Zealand have black following Maori tradition, and the Japanese football team wears blue [[http://www.kansas.com/sports/spt-columns-blogs/ask-sports/article1069113.html due to superstition.]]

* The colored belt rank system in most modern Martial Arts sports was created in order for practioners to tell who was at what level at a glance.

** The German military forces have since the 1920s utilized Waffenfarben ("corps color") as a border on shoulder boards or background on collar tabs to indicate the type of unit a soldier belongs to. Some of the colors have changed -- infantry was white during WWII, and is now green -- while others, such as the red for artillery units, have remained unchanged since their institution.

* UsefulNotes/RussiansWithRustingRockets takes it to the extreme with colour-coded undershirts. No, seriously. It started back in XVIII century, when sailors traditionally wore striped undershirts (telnyashkas) and so did the naval infantry. Their stripes were either deep-blue or black. Everybody knows that sailors are badass and marines are even more badass, so when, after UsefulNotes/WorldWarII, airborne corps were created, they received light-blue-striped telnyashkas. The first commander of airborne corps, Vasiliy Margelov, was a former marine, you see. Then, around 90's, the idea got around that you cannot be badass if you don't have telnyashka, so various forces started to introduce their own colour schemes.

** Soldiers do not wear a striped telnyashka--their undershirts are white.

*** Maroon Beret for [[ItsRainingMen Paratroopers]][[note]]Another that was adopted from the British during UsefulNotes/WorldWarII, beginning in 1943 when the a brigade of American paratroopers were made honorary members of Britain's Parachute Regiment and issued British berets.[[/note]]

* The UsefulNotes/WW2 German army colour-coded its soldiers in a very thorough Germanic manner. Epaulette, collar and lapel braiding advertised a soldier's arm of service at a glance. Nearly forty colours identified soldiers ranging from veterinary surgeons to assault engineers, but among the most common were white (infantry), red (artillery), pink (panzer arm, assault guns), russet brown (recconnaissance), and black (pioneers).

** In the 18th century it was typical for European armies to distinguish different regiments of the same arm by different facing colours (usually displayed on collars and cuffs of the coat) and button colours (brass or white metal). The Austro-Hungarian infantry used this system until UsefulNotes/WorldWarI with a total of 28 different ''Egalisierungsfarben'' including a shade called ''meergrasgrün'' ("sea-grass-green", not to be confounded with ''meergrün'' "sea-green" or ''grasgrün'' "grass-green"). Most armies seriously simplified their system of regimental colours however, for instance in 1881 the British infantry (other than rifle units) basically was reduced to four facing colours: dark blue for Royal Regiments (including Guards), white for English and Welsh regiments, yellow for Scottisch regiments, and green for Irish regiments.

** War Plan Orange: War with Japan. This was the most extensively developed and redeveloped of the color war plans. While the main basis of it (mustering up the Pacific Fleet and confronting the IJN head-on with a large surface navy before moving on the Home Islands) became outdated with technological advances in submarines and especially aircraft carriers (before and after the attack on Pearl Harbor), elements of this plan was eventually incorporated into the US's strategy in UsefulNotes/WorldWarII, such as the large submarine fleet that was to blockade the Home Islands (originally to buy time for the Pacific Fleet to mobilize, the subs ended up playing a key role in choking Japanese industrial capability) and not straying too far from land-based air cover (the "island-hopping" strategy).

*** Rainbow One: US defends the Western Hemisphere down to 10º south latitude against Germany and Japan (with the aid of as many neighboring countries as possible), while the UK and France remain neutral. Preparations were made for this eventuality after the fall of France, but fortunately the UK and the Free French forces remained firm until the Soviets and US became directly involved.
*** Rainbow Two: US is allied with UK and France; they support them in keeping Germany contained while rapidly striking against the Japanese in East Asia. Became irrelevant after the fall of France.

*** Rainbow Four: [[FromBadToWorse A scenario even worse than that of War Plan Red-Orange]]; the European Axis powers conquer the UK and France and seize their fleets, gaining naval supremacy in the Atlantic and enabling them to move against South America. The US immediately goes on a war footing, occupies all British and French colonial possessions and other critical locations in the Americas (with the help of Canada and the by-now terrified South American countries), and fights off the Nazis while diplomatically stalling Japan as long as possible.

** ''Fall Gelb'' ("Case Yellow"): The attack on the Netherlands, Belgium and Luxembourg in 1940.

* In Europe, where most of the older flags are just of one or two colours, republican and democratic movements had a tendency to use striped tricolours as their flags. The first such example was probably the flag of the Dutch provinces rebelling against Spanish rule in the 16th century, which is used to this day and is striped horizontally red (originally orange), white and blue. The abortive Belgian Revolution of 1788 used the colours black, yellow and red. The French Revolution combined the red and blue of the city of Paris with the white of the Bourbon dynasty, resulting in the vertically striped blue, white and red flag of today. As the revolutionary armies moved beyond the borders of France, they founded new republics with different tricolors, for instance green, white and red in northern Italy (now the national flag of all Italy) and green, yellow and red in the Helvetian Republic (when that became Switzerland again, they reintroduced their old bicoloured flag). Other such "radical" tricolors were the black, red and gold (yellow) flag of the German revolution of 1848 and the red, yellow and purple (claret) flag of the Spanish Republic used until it was crushed in the Spanish Civil War.

** Black: Politically, the color Black has a long association with anonymity, lawlessness, and "non personhood." Where colors or patterns of colors would signify personal identity and political allegiance, solid black, as the absence of color, meant the absence of allegiance. As far back as the Middle Ages, "black knights" carried no family crest or color on their shields, symbolizing their independence (or simply concealing their identities). Beginning in the 19th Century Black was adopted by Anarchist groups: the color of no country or government. More radical Anarchists groups often also use Black in conjunction with Red.

*** Black is also a colour strongly associated with Fascism, from the proverbial Black Shirts of Mussolini's followers and their British imitators, to the black uniforms of the German [=SS=].

*** In Organized Labour circles, Pink has negative connotations, being a lighter shade of Red and therefore associated with moderate or "soft" socialism. The epiphet "Pinko" was coined during the first RedScare of the 1920's to imply a person had socialist leanings without actually being a member of any organization or political group.
* The Québec student strikers of 2012 adopted the Red Square as their symbol against the 75% hike in tuition and in favor to the strike. As it gained in popularity both in the student body and the general population, other factions in the conflict tried to promote their own squares, with varied levels of success...

** Other students wore the Blue Square, which meant they were against the hike, but were also against the strike;
** At some point, columnist Richard Martineau suggested the Yellow Square, which meant that you would favor a ''smaller'' hike. It never caught on. In fact, the Yellow Square already had a significance before (though perhaps not publicized enough) as anti-nuclear stand in the province of Québec.

** When the government passed bill 78, which would restricts freedom of assembly, protest and picketing, especially on or near university grounds, writer Normand Baillargeon suggested the Black Square (to be worn WITH the Red Square) in protest of the violent repression suffered by student strikers since the beginning of the conflict, and as a symbol of grief over the death of democracy.

* Similarly, [[http://en.wikipedia.org/wiki/Electronic_color_code color coded electronic components]] as well as [[https://en.wikipedia.org/wiki/Electrical_code electrical wires]] are so electricians can tell their power and tolerances, and what colors to put on a given installation respectively at a glance.

** Green: local / metropolitan railways

* Tampa International Airport originally color-coded its numerous airlines based on the location of the airside terminal in which they typically docked: airlines in the northern terminals (C and D originally) were assigned to red, while airlines in the southern terminals (B and E) were assigned to blue. Because elevator banks, parking lots, ticket counters, and baggage claim areas shared this same dual color system, it served the purpose of preventing passengers from aimlessly wandering the airport searching for the facilities they required. While the color system still exists today, it's more or less [[TheArtifact lost its original fucntion]] as airlines get shuffled around on a fairly regular basis; thus, an airline that docks in one of the more northerly terminals may still find itself assigned to blue, or vice versa.

* Tampa International Airport originally color-coded its numerous airlines based on the location of the airside terminal in which they typically docked: airlines in the northern terminals (C and D originally) were assigned to red, while airlines in the southern terminals (B and E) were assigned to blue. Because elevator banks, parking lots, ticket counters, and baggage claim areas shared this same dual color system, it served the purpose of preventing passengers from aimlessly wandering the airport searching for the facilities they required. While the color system still exists today, it's more or less [[TheRelic lost its original fucntion]] as airlines get shuffled around on a fairly regular basis; thus, an airline that docks in one of the more northerly terminals may still find itself assigned to blue, or vice versa.

** On the flight deck of an aircraft carrier, where everyone has a very specific job and it's much too noisy to be heard, personnel wear different colored shirts denoting their job, be it fuel, maintenance, munitions, flight operations, etc.
*** [[http://www.navy.mil/navydata/ships/carriers/rainbow.asp US aircraft carrier flight deck personnel]]: "Explosive Ordnance Disposal" -- [[RedShirt Red]]. Ouch. As if it didn't sound dangerous already.
* On military ships, the colors of pipes indicate their contents:
** red = fire main (sprinklers/fire hose)