I have many of those 70mm cels, and I think I checked the date code on them once and if I remember correctly, the film dates from 1995 which is the year the cels were first sold (the SW ones were, anyhow. ESB and ROTJ were available later). I'll have to double-check those date-codes, though- it's been a while.

The color on them is good- the ROTJ ones maybe look a tad pinkish in the flesh tones (people who saw the triple-bill in 1985 have also said that the ROTJ print used then looked a bit pinkish) but they still look great compared to the pieces of film I have from a 1977 70mm SW print which is severely faded.