Artemy Lebedev

§ 107. Coding. Part two

June 22, 2004

Att'y: Are your eyes blue or green?
Waitress: Pardon?
Att'y: Blue or green?
Waitress: They change.
Att'y: Like a lizard?
Waitress: Like a cat.
Att'y: Oh, the lizard changes the color of his skin…
Waitress: Want anything to drink?

Hunter S. Thompson. Fear and Loathing in Las Vegas

Color coding

Although 8% of men and 0.5% of women are color blind, color coding is the major kind of coding.

The Columbia Encyclopedia. Color blindness

Where position and form cannot be changed and where symbols don’t work, color is brought into play, being a feature distinctive enough for an object to stand out. In some cases (for example, with a multi-conductor cable) one wire is different from another only in color.

A classical example of color coding is metro maps. One color is enough as long as there are few lines on a map. But as it gets bigger, additional colors are required. The 1908 London underground map is evidence to that:

The first underground map with color-coded lines

Waterlow & Sons, Ltd. Liverpool St Hotel map. 1908

In black-and-white printing one may use different hatch patterns instead of colors, but do so with care.

Traffic Signs (1954). Moscow: Moskovskaya Pravda
Identification of colors in road signs: black, yellow, red, green

The legend in the book on road signs is actually useless.

Tube black & white map. Transport for London, 2003

The legend of a modern black-and-white London metro map. All lines are clearly different, but there’s not a mention of color.

Color coding is widely used in analytical cartography.

Population density map. Redrawn from the original.

National Center for Geographic Information and Analysis (NCGIA). Population Density. 1994

Color is commonly used to code various kinds of the same product. In the past dairy products sold in glass bottles in Russia differed in the color of foil lids: milk—silver foil, acidophilin—blue, kefir—green, baked milk—crimson, etc.

Around the world before boarding, during the flight and after arrival travelers order whisky bearing in mind the colors of the label that codes the age and quality of the drink: the Red Label (5 years), the Black Label (12 years); the knowledged may want to have the Gold Label (18 years) or even the Blue Label (17 years + the hype).

Black caviar is sold in cans with lids of three colors. The cans don’t bear any signs of difference (it’s all “sturgeon caviar”), but the type of fish is coded in color, which explains pretty well the difference in price.

Beluga or sterlet



Audio coding

A car horn allows one to convey the entire range of messages from “honey, I’ve come” to “watch your way, dork!” Audio codes are used in computers (mistake alarm), telephones (tone dialing), airplanes (sound signal systems for pilots and crew members) and so on.

One of the most successful implementations of audio coding can be heard in the Moscow metro. A male voice announces stations when the train is headed towards downtown, a female voice—when it moves from the center to city outskirts (sort of a mnemonic rule: the boss calling you to work, the wife calling you home). On the circle line a male voice is heard when the train moves clockwise and a female one when it runs counter-clockwise. The purpose of this is to make wayfinding easier for the blind.

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