The colour pallete for the environnment would be dark, but there owuld also be colour palletes for gore that would be implimented into the game, for example blood reds, flesh colours etc to inicate something bad has happened within the city, not just the flood.
The art style would be a mix of modern and art deco.
Insane enemies within the game would look like they have been stuck in the ruined city for a long time with tattered clothes or hand made clothes that they have made themselves, similar to Mad Max. The physical appearance of the characters would look disturbing as though they have been exposed to something.
During the trailer itself, the camera movements would appear cinematic in how it moves thorugh the environment giving it a cinematic style.
For the main/playable character, I would prefer it to be a female. I would prefer it this way as it is its a generic cliché that the main character is male. There are only a handful of games where the main character is only playable as a female.
For weapons in the game, the player would have to be rescourceful and find potential weapons within the environment - the game would be heavily melee weapon based howver there would be guns but they would be in limited suply and to be used in extreme circumstances.