the reason ANH's take on luke's saber was white-ish was 'cause the FX guys and lucas were Noobs at the time. they were dropping the "plasma" over a Lucite Rod (used for the actual fencing scenes), and didn't quite match it up. even in his anniversary edition, they weren't right, yet. even vader's saber was only mediocre. you can still see the jump when they have the actors freeze so they can switch out to the rodded handles. and what do you mean the green was wrong? you mean in RoJ? I heard that was a screw up in the FX department or something, and lucas rolled with it, making the Green Blade the "master's edition" color (though you can VERY obviously see the young padawans sporting a mix of green and blue blades in Ep 2's academy scene)
and, for those who HAVEN'T heard yet; the reason Mace's saber was purple? so Samuel L Jackson's momma could spot him in crowd scenes