A color code is a system for displaying information by using different color

Color

Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

s. Color codes are often difficult for color blind

Color blindness

Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired...

 and blind people to interpret.

The earliest examples of color codes in use are for long distance communication by use of flags, as in semaphore

Flag semaphore

Semaphore Flags is the system for conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags; it is read when the flag is in a fixed position...

 communication. The United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 adopted a color code scheme for such communication wherein red

Red

Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...

 signified danger

Risk

Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...

 and white

White

White is a color, the perception of which is evoked by light that stimulates all three types of color sensitive cone cells in the human eye in nearly equal amounts and with high brightness compared to the surroundings. A white visual stimulation will be void of hue and grayness.White light can be...

 signified safety

Safety

Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...

, with other colors having similar assignments of meaning.

As chemistry and other technologies advanced, it became expedient to use coloration as a signal for telling apart things that would otherwise be confusingly similar, such as wiring

Electrical wiring

Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to...

 in electrical and electronic devices, and pharmaceutical pills

Pill (pharmacy)

A pill is a small, round, solid pharmaceutical oral dosage form that was in use before the advent of tablets and capsules. Pills were made by mixing the active ingredients with an excipient such as glucose syrup in a mortar and pestle to form a paste, then rolling the mass into a long cylindrical...

.

The use of color codes has been extended to abstractions, such as the Homeland Security Advisory System

Homeland Security Advisory System

In the United States, the Homeland Security Advisory System was a color-coded terrorism threat advisory scale. The different levels trigger specific actions by federal agencies and state and local governments, and they affect the level of security at some airports and other public facilities. It...

 color code in the United States. Similarly, hospital emergency codes

Hospital emergency codes

Hospital Emergency Codes are used in hospitals worldwide to alert staff to various emergency situations. The use of codes is intended to convey essential information quickly and with a minimum of misunderstanding to staff, while preventing stress or panic among visitors to the hospital...

 often incorporate colors (such as the widely used "Code Blue" indicating a cardiac arrest

Cardiac arrest

Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...

), although they may also include numbers, and may not conform to a uniform standard.

Examples

Systems incorporating color coding include:

• Artillery shells and other munitions, which are color coded according to their pyrotechnic contents
• Bottled gas
  Bottled gas
  Bottled gas is a term used for substances which are gaseous at standard temperature and pressure and have been compressed and stored in carbon steel, stainless steel, aluminum, or composite bottles known as gas cylinders.-Gas state in cylinders:...
  
  es
• ColorCode 3D
  ColorCode 3D
  ColorCode 3D is a newer, patented stereo viewing system deployed in the 2000s that uses amber and blue filters. Notably, unlike other anaglyph systems, ColorCode 3D is intended to provide perceived nearly full colour viewing with existing television and paint mediums.-Technology:One eye receives...
  
   stereo image system using blue/amber viewing glasses
• Electrical wiring
  Electrical wiring
  Electrical wiring in general refers to insulated conductors used to carry electricity, and associated devices. This article describes general aspects of electrical wiring as used to provide power in buildings and structures, commonly referred to as building wiring. This article is intended to...
  
   — AC power phase, neutral, and grounding wires
• Electronic color code
  Electronic color code
  The electronic color code is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others...
  
   — for electronic components
• Fire extinguisher
  Fire extinguisher
  A fire extinguisher or extinguisher, flame entinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations...
  
  s
• Handkerchief code
  Handkerchief code
  Handkerchief code or hanky code is color-coded system, employed usually among the gay male casual-sex seekers or BDSM practitioners in the leather subculture in the United States, Canada and Europe, to indicate preferred fetishes, what kind of sex they are seeking, and whether they are a...
  
  
• Jumper cables
  Jump start (vehicle)
  A jump start, also called a boost, is a method of starting an automobile or other vehicle powered by an internal combustion engine when the vehicle's battery has been discharged. A second battery is temporarily connected to provide starting power to the disabled vehicle...
  
   used to jump-start a vehicle
• Navigation light
  Navigation light
  A navigation light is a colored source of illumination on an aircraft, spacecraft, or waterborne vessel, used to signal a craft's position, heading, and status...
  
  
• Sea mark
  Sea mark
  A sea mark, also seamark and navigation mark, is a form of aid to navigation and pilotage aid which identifies the approximate position of a maritime channel, hazard and administrative area to allow boats, ships and seaplanes to navigate safely....
  
  
• Characteristic light
  Characteristic light
  A light characteristic is a graphic and text description of a navigational light sequence or colour displayed on a nautical chart or in a Light List with the chart symbol for a lighthouse, lightvessel, buoy or sea mark with a light on it. The graphic indicates how the real light beacon may be...
  
  
• Optical fibers
• PC connectors and ports
• Ribbon
  Ribbon
  A ribbon or riband is a thin band of material, typically cloth but also plastic or sometimes metal, used primarily for binding and tying. Cloth ribbons, most commonly silk, are often used in connection with clothing, but are also applied for innumerable useful, ornamental and symbolic purposes...
  
   colors see: :Category:Ribbon symbolism
• Three-phase electric power (electrical wiring)
• Traffic light
  Traffic light
  Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...
  
  s
• 25-pair color code
  25-pair color code
  The 25-pair color code is a color code used to identify individual conductors in a kind of electrical telecommunication wiring for indoor use, known as twisted pair cables . The colors are applied to the insulation that covers each conductor...
  
   — telecommunications wiring
• Underground utility location
  Utility color code
  Utility location is the process of identifying and labeling public utility mains which are underground. These mains may include lines for telephones, electricity distribution, natural gas, cable television, fiber optics, traffic lights, street lights, storm drains, water mains, and wastewater pipes...
  
  
• Web colors
  Web colors
  Web colors are colors used in designing web pages, and the methods for describing and specifying those colors. Hexadecimal color codes begin with a hash ....
  
  for HTML color codes