The Orange Catholic Church was a fairly popular religion in the Earth Federation and other human interstellar polities prior to the Ascension War. Since then, it has been mostly subsumed into the Cult of the Emperor.
During Gehenna, once the existence of vampires, werecreatures, and mages became common knowledge, all sorts of other secrets came out. The extent to which various supernatural factions had infiltrated and manipulated the Roman Catholic Church over the centuries became a bit of an embarassment and a public relations disaster for the church. As people were flocking to other denominations during the apocalyptic struggle for the soul of mankind raging all about them, people were deserting Catholicism in droves. To stem the tide of defections from the faith, the Pope called an ecumenical council meeting in Rome, what came to be known as the Third Vatican Council, or Vatican III. Anglican/Episcopalian representatives were also invited, as that church was also seeing its membership dwindle in the face of Gehenna's revelations about its past, and many participants hoped the Schism born in Henry VIII's codpiece could be ended at last and the two faiths reintegrated into one.
But rather than put the faith back together, the council ended up splitting the faith into three major branches, the Orange Catholic Church, the New Roman Catholic Church, and the Third Vatican Catholic Church.
The New Roman Catholic Church tried to ignore the sweeping changes in the universe and avoid reform, remaining much as it was before Gehenna. The Orange Catholic Church, so called because it was largely made up of Anglican "Orangemen", many from Northern Ireland, embraced the new realities, reaching out to the awakened and the shapeshifters and offering even Vampires a path to redemption and a closer walk with God. And the Third Vatican Catholic Church sought to purge the new supernatural element from society altogether. The Third Vatican Catholic Church held that the recently-revealed supernatural creatures were satanic in nature, and no good could come of them or involvement with them. Third Vatican Catholics sought to separate themselves from awakened society and create a community of unawakened humans only. This belief structure has surprisingly been rather resilient over the centuries, and despite frequent massacres of members and in the face of occasional attempts to suppress the faith under the Federation, the church never quite went away.
Orange Catholics, by contrast, taught that mage powers and werecreature abilities were gifts of the Holy Spirit, to be used to work God's will in the world. The Technocracy and its New World Order branch saw in this Orange Catholic Church a chance to resume their past control over society through religious orthodoxy. While the proliferation of new cults and denominations brought out by Gehenna made a single government-enforced orthodoxy impossible in the new Earth Federation, the Orange Catholic Church was subtly encouraged and subsidized, becoming by far the largest faction to emerge from what had once been the monolith of Catholicism.
When the Caal Invasion brought the Federation crashing down, and a new round of doomsday cults proliferated, a single event changed the Orange Catholic Church forever. Pierre Villars, the governor of the New Paris system, went naked into the Orange Catholic Cathedral in his capital city and began self-flagellating himself with a leather whip. He pledged his life and that of his subjects to the Church and God's Will if only he would spare them from the Caal Armada bearing down upon their world. When the Caal fleet passed by New Paris without incident, bypassing it en route through the Digital Gate to Avalon, this "New Paris New Passover" became the first major miracle of a new faith. When Vin Dane led the fleet that destroyed the Caal over Avalon, he became the focus of worship as the new God-Emperor of Mankind, and the Cult of the Emperor was born. The role of the New Paris New Passover in the origin myth of the new faith ensured that Orange Catholics would be subsumed into the new faith in droves, and Orange Catholic dogma became the core of the new faith as well.