User blog comment:Psionicblades/Debate: Why do Dark Templar use Void Energies if the Void is corrupted by Amon?/@comment-31277203-20180129041816

I felt Ouros was exaggerating when he was telling Raynor, Kerrigan, and Artanis that the Void was an extension of Amon's will. If that was true he would have been able to control the Nerazim and the Tal'darim. Alarak made it clear to Artanis that as the Tal'darim don't use the Khala, Amon cannot bend them to his will. Amon could control parts of the Void (as we saw via the Void shades), but certainly not all.

For the Void as a religion, I don't think it's really like that, maybe they felt the Void was the place where the "afterlife" exists or something. It's not like we knew about what Amon did to the Void until LotV anyway.

For their powers being green, it's probably because exposure to Void energy was different compared to regular psionic energy (Khala or no Khala). The whole being able to control it only proves that Amon never corrupted all of the Void to his will and all that.