When The Dark One was just another Goblin, he was the centerpoint of the hopes and dreams of millions of Goblins who wanted to break the bonds of their servitude. When TDO's mortal body died, the faith of millions of Goblins hoping and believing that TDO could help them was the faith that created the Theosophic particles to emanate from TDO's newly created singularity. As this faith was not connected to any existing Pantheon (who knows if any of the other Pantheons had the option to adopt this newly created being as one of their own but passed on it), the Quiddity chose a new color according to QCD's advanced color theory.