Wikipedia
Indiglo is a product feature on watches marketed by Timex, incorporating an electroluminescent panel as a backlight for even illumination of the watch dial.
The brand is owned by Indiglo Corporation, which is in turn solely owned by Timex, and the name derives from the word indigo, as the original watches featuring the technology emitted a green-blue light. The Indiglo name was originally developed by Austin Innovations Inc.
Timex introduced the Indiglo technology in 1992 in their Ironman watch line and subsequently expanded its use to 70% of their watch line, including men's and women's watches, sport watches and chronographs. Casio introduced their version of electroluminescent backlight technology, Illuminator, in 1995.
Indiglo backlights typically emit a distinct greenish-blue color and evenly light the entire display or dial. Certain Indiglo models, e.g., Timex Datalink USB, use a negative liquid-crystal display so that only the digits are illuminated, rather than the entire display.
Hunter Fan company has also incorporated Indiglo technology in lighting the displays on many of its thermostats.