Actually, by 1985 I'm pretty sure 70mm prints would have all been low-fade. I saw an original 70mm of Ghostbusters back in 2010, it was beat up and ridden with splices, but the color was fully intact.

But how many 70mm prints still exist, I don't know. Only 7 theaters in the US/Canada played it in 70mm on opening weekend, so I'm guessing only a handful of prints were ever struck.

http://www.thedigitalbits.com/columns/history-legacy--showmanship/going-back-in-time-back-to-the-future-30th

I have no idea if the image here is from a small strip of film, or if it's from a complete print some collector has. I doubt we'll ever know.