How might the novel’s flavor have been changed if Pi’s sole surviving animal were the zebra or Orange Juice? (We assume that if the hyena had been the only surviving animal, Pi would not have lived to tell us his story.)

I think your question addresses the idea of Richard Parker's uniqueness. Certainly the image of a bright orange striped tiger elicits primal and emotional reactions in people. The Tiger is impressive in his ferocity but, ironically, is reduced to the very unnatural situation that Pi is in. He reacts as a tiger might and Pi reacts with his own unique understanding of animals and philosophy. Pi also anthropomorphizes Richard Parker in a way that cannot be done with any other animal on the boat. Both Richard Parker and Pi have a unique chemistry together that helps make the story what it is.   

Among Yann Martel's gifts is a rich descriptive palette. Regarding religion he observes the green elements that represent Islam and the orange tones of Hinduism. What color would Christianity be, according to Pi's perspective