DON'T DIG UP OLD GRAVES
Fluorescent lighting
Instead of making the bar seem fun and cosy, it should feel more sterile. This should be subtle but strong enough to make the space feel off. As the film progresses, this will evolve into a more abstract, colourful look motivated by the characters' emotions.
Contrast and grit
Deep blacks and areas without any light will give a strong tone to the film. When dreaming or imagining we don't see all the details. This shouldn't be too abstract but strong enough to create the feeling of uneasiness and the darkness that is consuming Jamie.
Strong colour
Colour should be used to reflect the emotions of Jamie and Ally as well as linking the spaces they're in to tie them together. Making the light 'spill over' from one location to another will also be a hint that what we're watching is in Jamie's head.