@Adywan

If the core of vader's saber was white as you say, it would match the vertical white slits behind the two combatants.

I took a screen cap from the original 77 ' launch trailer that is on the 2004 DVD bonus disc.

As you know the trailer was presented in 16:9 standard def(i.e better quality than either VHS or laserdisc).

It is also fairly representative of how the film looked(unlike the teaser trailer)

here it is:

Now if I zoom in just to focus on an area of interest you can clearly see the distinction between white (of those slits in the wall)and the mild pinkish/mild red tint of the saber:

And here is the trailer shot side by side with the equivalent frame from the 2004 DVD:

Are they different--yes.

But it's not like the 2004 DVD made vader's saber green!