Quoted from Swainer80:my guess is that it's just the plasma that was used at the time. They're just a updated brethren of alphanumeric displays, those are plasmas too and orange. under the history tab it shows a black and orange plasma display screen https://en.m.wikipedia.org/wiki/Plasma_display
And earlier, like the 6 and 7 digit early Stern/Bally displays.