That green and blue.
From there Fincher would make two amazing films Se7en and Fight Club, and these two films would turn him into one of the biggest directors today. You can see in Se7en the way he directs just two or three people talking and then turns just that into something cinematic and intense. Fincher is known to not really use handheld shots and always keep the camera locked onto a tripod or a track. He knows when to cut and which shot to use to build up tension until it all falls. You can clearly see this throughout Zodiac and the anxiety you get from watching the film. Throughout the film Fincher uses some beautiful insert shots of detectives scrambling through notes and puzzles left behind by the killer. And you can see how that carried over to Netflix's House of Cards and in an odd way there's also a serial killer in that show too.
As time passed Fincher further toned his style but this time through his production design and the colors used in his films. Starting with Panic Room in 2002, Fincher's films started to get this green and blue tint. This was only expanded when he made The Social Network, The Girl With the Dragon tattoo, and now Gone Girl. Fincher combines these elements and just from watching his films you know exactly what he wants, and no matter how many takes it takes, he will get it.