Costumes in Focus

In the poster, Will Smith is wearing a blue suit, with a blue tie, along with sunglasses that have blue light reflected in them, As blue is a "masculine" colour that reinforces security and is a primary colour, it reinforces the fact that he is the main protagonist. 

 Here Margot Robbie is dressed in an expensive formal red dress. The colour red connotates lust, as it shows Will Smith (or any other main character) could be attracted to her. The fact that it is expensive conforms to genre as in crime dramas, characters are either very rich, or very poor.

 In both of these shots Will is wearing a casual suit, without a tie, which implies he is wealthy as he wears a suit as casual wear. Margot is shown again wearing a formal dress.

 In this shot, Will is wearing a waistcoat, throughout the film the majority of the shots are in formal attire, to reinforce his wealth.

I think that the costumes used here are effective as they portray the genre clearly and also show the wealth of the characters.