[mrtomservo]

I agree -- color bars pre-printed on tractor-feed paper would have used a Pantone ink, maybe a tint of 290 for blue, or 358 for green. Mills wouldn't have likely used a C+M+Y build: Why pay for three inks (and the potential for misregistration) when you can just use one? There might have even been a special machine to print the lines at regular intervals, and not run through a traditional offset printing press.

Pantone inks in specific, and printed colors in general, don't convert precisely to RGB. Ambient light reflects off paper to your eyeballs; a screen beams light into your eyeballs.

It's a nice little nostalgic thought exercise, though.

[Symbiote]

It wouldn't necessarily be a Pantone shade — that costs extra, and any mid-green is adequate.

The pictures on the Wikipedia article show several shades of green: https://en.wikipedia.org/wiki/Continuous_stationery

[zokier]

Of course if you are really interested you can just buy a box of green-bar paper. It's still in mass-production. E.g. Staples carries it https://www.staples.com/Staples-Green-Bar-Computer-Paper-14-...

The inks probably might have changed over the decades, so it might look different than genuine '70s paper. But on the other hand I'd imagine there are literal tons of green-bar paper sitting in archives from various times and sources if you want to do some archeology