I've already given my lecture about serving the story and not doing something just because you can, so now I'll take a moment to tread that fine line between fan and fanboy *Shudders*:

Yes, changing the laser color may seem like a minor, insignificant change (So did Greedo shooting first), but think of the larger picture in terms of canonicity. Laser color is a marker of what kind of technology is powering the weapon. If you change the laser color you have, indirectly, change what technology makes up the weapons systems on the Imperial Walker which has been outlined in countless Star Wars tech manuals prior (I think).