The great purpling. Streetlights turning purple. Not really enough to call a Purple Reign, I don't think -- just a small percentage in each city. The culprit is LEDs. By combining red, green, and blue, you can make white. By replacing red and green with yellow, you can get white with only 2 LEDs. Replace the yellow with a phosphor coating that makes yellow from blue light, and you get white with only a blue LED. But if manufacturing defects allow for the phosphor coating to malfunction after installation, you get blue streetlights. Well, apparently the wavelength chosen for this LED is short enough to be perceived as purple.
It's not Halloween, it's not because your football team wears purple, it's not a conspiracy, and it's not the city trying to change how "romantic" your city feels and ending up with something weird. It's not intentional.
The weird, worrisome mystery behind America's plague of purple streetlights
