OT-ish: Blue LEDs

[Jules Richardson]

Does anyone know when blue LEDs first became commercially available? The
pair of Apollos that arrived at the museum yesterday both have
rectangular blue LEDs fitted alongside the amber and green on the front
of the machine - the systems date from 1990 though...

It's possible that someone's fitted them years later of course! They
certainly make the systems stand out though :-)

cheers

Jules