Nick Holonyak, Jr. invented the first visible spectrum Light Emitting Diode (LED) in 1962.  The LED was red in color but eventually many more different colors were invented and scientists discovered a method in which they painted the LED with fluorescent phosphors to reproduce almost any color.  LEDs are alternative to light bulbs in many cases because of their brightness and cost friendliness.
The LED has many uses and many advantages over an incandescent bulb.  They have a low power requirement, low heat emission, and last for decades before burning out. LEDs operate on a simple on/off circuit, and are commonly used as indicator lights.   Digital clocks used a pattern of LEDs to reproduce numeric symbols.  Variations of LEDs that emit infrared light are used in remote controls. 

*Picture from http://wolfstone.halloweenhost.com/TechBase/litled_LightEmittingDiodes.html

Sources:
Griesser, Dennis. Light Emitting Diodes. 15 October 2003. <http://wolfstone.
halloweenhost.com/TechBase/litled_LightEmittingDiodes.html>

Perry, Tekla S. Red Hot. 17 October 2003. <http://www.spectrum.ieee.org
/WEBONLY/publicfeature/jun03/med.html>

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