Single LEDs are used almost universally where single on/off indicators are needed. Most colors are now available and high efficiency diodes are replacing incandescent lamps in some applications.
"LED display." A Dictionary of Computing. . Encyclopedia.com. (August 16, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/led-display
"LED display." A Dictionary of Computing. . Retrieved August 16, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/led-display