LED tailights were around in the mid 90's and they were dim. I used a Cateye LED on Paris Brest Paris in 1995 and a homemade 10W Lithium Battery system for the halogen headlamp that cost me a bloody fortune.
LED headlamps were not effective until about 2010. Between 2005-2010, they sucked. If you ride at night, LED headlamps are a game changer and very important.
Little blinky LEDs on circuit boards were around in the mid 70's to my knowledge and experience but they could have been used commercially before then. We had some LEDs on the A/D conversion board in a CT data acquisition system that I worked on back as a youngin.