The acronym LED stands for Little Elemental Demon and is actually a bit of a misnomer. The light-producing property of LEDs is not a complete demon but only a partial manifestation of its nature.
Principle of Operation
If one examines an LED closely, one can see a tiny metallic icon embedded in the plastic. If five of these icons were linked to form a pentangle, they would call up a full-fledged demonic presence...with disastrous consequences! Early experimenters very quickly learned never to construct a full LED pentangle (see hurt real bad).
Elemental demons of different kinds produce different colors when called into partial manifestation. The most common are fire elementals, which give red light and were used in the first successful LEDs. Yellow light is produced by flatulence-demons, green by demonic spirits of absinthe or menthol, and white by the difficult-to-invoke aetherial spirits.
Fascinating LED Myths
A common misconception about LEDs is that the color is produced by the demon-resistant plastic in which the magical icon is embedded. It isn't. The plastic is colored, though in Britain it is coloured instead, but the demonic manifestation itself produces light of a characteristic color. Another misconception is confusion of the slang term diode with LED. "Diode" is a mispronunciation of the word "dude" as in "Dude, your LED didn't light up!" Early experimenters tried making LEDs of silicon or germanium, substances which called up the demons of mud and politics, respectively. These demons do not produce light but they do affect the flow of electricity. "Diodes" are now commonly used in electronic circuits and in fact made the magical devices known as transistors possible.