Indigo is a dark blue color based on the traditional dye of the same name. The dye was discovered around 6,000 years ago and is traditionally used by multiple civilizations including Peru, Mesoamerica, China, Japan, Egypt, Iran, India, Africa and the indigenous peoples of North America. Indigo was well known to the ancient Romans and Greeks where it was imported from India as a luxury. Indigo dye can produce a variety of colors but is primarily a dark or light blue that is often slightly green or violet. In 1986, some programmers created a list of color names for a unix system known as X11. Having no background in color theory, they placed indigo as a dark purple. This list was later used by HTML and CSS standards that remain in place to this day. These standards are used by millions of designers and digital artists such that the color name indigo is now strongly associated with dark purple or violet. As such, a few programmers accidentally repurposed a color name that was known to civilizations for thousands of years. The following are common types of indigo color
Imperial Blue
#002395
Indigo
#00416A
Faded Indigo
#006ca9
Neon Indigo
#091f92
Dark Indigo
#1f0954
Japanese Indigo
#264348
Japanese Indigo #2
#274447
Indigo #4
#324680
Mood Indigo
#353a4c
Indigo #2
#374874
Kachi Indigo
#393e4f
Indigo #3
#3a18b1
Violet Indigo
#3e285c
Indigo #2
#49516d
Web Indigo
#4b0082
Royal Indigo
#4e4260
Electric Indigo
#6F00FF
Jeans Indigo
#6d8994
Tropical indigo
#9683ec
Above: note the difference between Web Indigo and Indigo. This standard color name is completely detached from the traditional color. This misrepresentation resulted from the random selection by a programmer working on an operating system in 1986.
Associations
Indigo was historically a common and important dye such that it is associated with vintage clothing in many cultures. For example, indigo kimono in Japan have an Edo-era feel to them. Indigo is immersed in history, tradition, culture and folklore such that it has a different meaning in each culture.As a natural dye, indigo has an organic and earthy feel. For this reason, it was popular amongst the hippie subculture of the 1960s. This is perhaps its strongest current association.Notes
Some indigo dyes look purple when faded by sunlight e.g. the color of Tropical Indigo above.Indigo is a natural dye but synthetic versions also exist.Blue jeans are often dyed with indigo giving them their characteristic blue color.