The blue LED was supposed to be impossible—until a young engineer proposed a moonshot idea.
My favorite thing about widely-available blue LEDs was the effect on TV scifi.
Watch the Star Trek shows made in the 1980s and 1990s and the tricorders, alien gadgets, and other props were always twinkling with red, yellow, and green LEDs to look futuristic. A generation later and every single hand prop on 2000s Doctor Who, Torchwood, etc. glowed and twinkled blue because the LEDs had just become cheap enough for prop makers, but weren’t yet widespread in day-to-day life so the viewers were seeing something strange and unusual.
Now every color of LED imaginable is just common and whatever, but for a good stretch of time glowy blue became the standard “scifi” color just because that particular tech happened to turn up at that particular time.
