20 Mind-Blowing Facts You Didn't Know About Zodiac (2007)

The eagle-eyed viewer may have noticed something about the film's colour palette. The colour blue is heavily featured in the majority of shots. This isn't unusual per say, most films of this genre make use of blue camera filters to give a cold, dark feel to the piece. Yet Fincher went one step further, as he always does.

Not only does he use the standard blue camera filter, the content in front of the camera is, more often than not, blue. The Zodiac's letters are written with blue ink, the first letter is even read by the Chronicle's editor who sports a blue shirt. The cocktail Graysmith shares with Avery is a blue drink, Arthur Leigh Allen's overalls are even blue.

The colour appears almost constantly throughout the film, but it's not just an aesthetic choice. One of the more promising leads in the case revolved around what Graysmith refers to as 'The Water Theory'. The cartoonist notices a pattern, with the attacks taking place near bodies of water, such as Lake Berryessa.

The continued usage of the colour is Fincher's way of bringing the theory to the forefront of viewers minds. Constant, but subtle references to the theory gives added weight to the theory.