OKAY, injecting some humor here. No offense to anyone.
Crewman, "It's not possible blue LED's do not belong in that high voltage panel!"
Chekov, "Ah, but LED's vere invented by a Russian Scientist (Oleg Losev) in 1927."
Spock, "While he was the first to research them and propose the correct theory of how they worked, even using them in a practical application of electroluminesence they were not in fact common. They were appearing in practical electronic components in 1962, however, until 1968 visible LED's were $200 per unit, a hefty sum. Also, the first visible LED's were of low intensity and limited to red. The first blue LED's were developed at RCA in 1972 although the first high brightness blue LED's were demonstrated in 1994 by the Nichia Corporation. Since crewman we are now in the 23rd century their existence on the Enterprise is not in question!"