From an EU perspective, we know that the Nightsisters had resurrection-like magics, and we know that Palpatine cowed them during the Clone Wars.
But the key here is that even without knowing that, it still works. The green is a lovely evil shade that takes us off the usual blue-red Jedi-Sith spectrum and implies that Palpatine has tapped into even more mysterious arcane methods to bring about his return.
I think that this, coupled with changing the vats to have Palpatine bodies, uses all of the established Star Wars rules to far better justify Palp’s return:
Cloning technology + ‘many abilities some consider to be unnatural’ + Nightsister magics => ‘More than a clone, less than a man’.
And if changing Ajan Kloss to Naboo works out, the green here can also signify Sheev being reborn in the color of his home since Naboo is mostly known for its greens. Naboo everywhere. Just need to fit in some gungans somewhere to complete the masterpiece!