I pride myself on my ability to analyze
I think Ive unwraveled most of this flash. I agree mostly with lil-kimi (2 comments below me) so i'm not going to repeat what he already said, I'll focus on where I disagree with him.
The parts with a red background are his present, on his way to the death. The gray backgrounds are flashbacks into his life. The first scene sets the mold for the rest of the movie. It's people going down one of those things(you know what i'm talking about) away from the light and into the darkness. I'm not sure what the scene where he is crying over the dead body (a child?) but because there are people chanting catholic prayers in the background, perhaps this symbolizes the death of catholicism the child being baby Jesus. This is reinforced in the scene where the man walks down the hill into darkness leaving behind him a cross falling down. The man might be preacher based on the scene with the dissappearing cross when he is at a lectern. He might have commited suicide in despair at his religion dying. The tower with the arrows symbolizes judgement to heaven or hell, for every one person going up to heaven there is three going to hell. when the lights come on he is being judged, and despite turning away from god and commiting suicide (which is a mortal sin) he is sent up to heaven. He is forgiven.
Oh and I forgot in the very beginning the candle going out of course symbolizes death and the flashback where he rings the doorbell handing out fliers that say "Are You Good Enough?" means he hates himself for asking others if they're going to heaven when he's not sure he's going there himself.
Great movie.