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.

The 04SE green blade was just a complete and inexplicable screwup.

That scene could have been "corrected" in the same way as the duel in 2004, but for some reason it was never done. Even in 2011, all they did was fix the green saber.