I dont see why they didnt just do the start like the novel where he asks for all these priveledges and the angel is gawking all over. Doing it flashback style a lot of context is lost and it doesnt look as impressive, it just makes it feel like convenient thing added later on.
@ildaggerll technically, the purest fire would be colorless, while orange flames are due to soot, any light a fire gives off is inefficiency. Though if it can burn everything including light, it would be black. But if you want to keep it within the realms of actual fire then closest to purple is more pure(a step above blue), hydrogen fire is probably the purest known fire as it burns in the ultraviolet spectrum which is a step above purple.