The white blade was a consequence of contrast/gamma boosting on the video transfers. From what I've seen of theatrical prints, it was light blue in every shot.
I assume the greenish white in the 97SE recomposites was either due to the color correction being botched, or possibly the glow elements having faded and not being able to be fully corrected back to the original color.
We discussed this at lenght in http://originaltrilogy.com/forum/topic.cfm/Complete-Comparison-of-Special-Edition-Visual-Changes/topic/11927/page/12/ a few years ago. To be honest I'm still not sure what the hell they did back then, the compositing is so technically inept in the Special Edition I can't really tell if they used original elements or just re-rotoscoped them from scratch. (it clearly was the ILM B-team handling it) The reason I find it hard to tell is that all the quirks and shortcomings of the original compositing are still there but with new ones added on top. Apparently it was so poorly redone that most people, who don't remember or are newcoming fans, still to this day think they're seeing the original lightsabers when they're watching the SE of the first film.
Also, the only lightsaber shots that were remade for the 1997 SE was the one in Ben's hut and those aboard the falcon and they were far from an improvement. They eliminated the dupe grain and that was all. The cantina saber and the duel was remade in the DVD version in 2004 with Ben suddenly wielding a Mace Windu saber in certain shots.
Just a few examples, one is a faded original, the other a "state of the art".
1997 Special Edition
1997 Special Edition (Ouch, that's gotta hurt)
1997 Special Edition
^ Instead of repositioning the original crude animation (it's clear it was meant to be positioned where the laser hit the blade) the animators decides to repaint the original effect - paint where there before was ship interior.
I guess it's possible the crude animations seen aboard the falcon are separate elements and that they were done by that ILM guy who did the laser bolts, I don't recall his name at the moment (ashamed) but I doubt it.
I don't know but it's doubtful the original elements have even survived for recompositing. For Star Wars the lightsaber effects were outsourced to a company named DePatie-Freleng Enterprises or more specifically they were done by an animator named Nelson Shin, who also did the animation work on The Pink Panther. An interesting interview with the fellow:
AR: Nelson, it's not just cartoons is it? Apparently you also came up with the idea of the light saber for Star Wars? Exactly how?
NS: At that time, I was working for a company in the States, and my manager called me in one day asking if I could work on the effects of the live action for the film. So what we did was they brought in the Star Wars clip causing effects, and asked me if I could draw the light saber with the animation. I first got to learn about a device called the rotoscope, in which you put the film in the camera, shed the light on it, and then it shows on the animation table. Then, you trace the live action drawing parts. People from Lucas Film came to pick it up.
I explained to them since the light saber is light, and the light should look a little shaky like fluorescent tube. I suggested that when printing with optical printer, one frame should be inserted so that one could be printed much lighter than the other. By that way, it would look like a fluorescent tube or laser. I also asked them to pass on the information that when adding the sound, a degauser, which is used in deleting tapes, should be placed on the top. Then, this device would make sound, because it has magnetic field like light streaming.
So that's how the light saber came to life. In fact, I did not need one month, but finished it in a week. My company was very surprised because I finished it within one week. When people from the Lucas Films picked it up, they put me into the director's chair. They showed the product from behind with over the shoulder on the small screen, and it was excellent. I did not expect such effects at all. The team had followed my advice on adding sound, and on using an exacto knife to cut the paper to give a very sharp look of light.
They asked my opinion about it. Since my vocabulary was not good at that time, I said, oh, it's ok. I should have said, oh, it was really great. They said it was more than ok. At that moment, I felt that I should learn how to express my feeling with more excitement. Lucas film sent some people 3-4 times to scout me with generous offers. But at that time because Star Wars was just released and I didn't realize it would expand into a very long series. I refused their offers because I was not sure about moving into a new field.
I'm sorry Nelson, a couple of computer nerds up in Marin County have since replaced your work.