after the reveal this episode i think this poster just revealed who the NHI killer is
spoilers i think itstanya
harry and laguerta are on the right in blue area and aaron and tanya are on the left side in the red area and finally dexter right in the center .
i the red and blue is a refrence to the red and blue lights of police cars since everyone in this image works for miami metro
laguerta and harry and trying to catch the NHI killer and are good which explains why they are together on one side where as now that we aaron is a killer and is on the left side with tanya .
this also makes more sense since dexter is in the middle which probably represents that he is a killer but also good .