Memento chronicles two separate stories of Leonard, an ex-insurance investigator who can no longer build new memories, as he attempts to find the murderer of his wife, which is the last thing he remembers. One story line moves forward in time while the other tells the story backwards revealing more each time.
The most significant manifestation of Leonard's injuries is that his short-term memory has been destroyed; he is incapable of retaining any new information, and must resort to copious note-taking and Polaroid photographs in order to keep track of what happens to him over the course of a day (he's even tattooed himself with a few crucial bits of information he can't get along without). That's exactly why the film can be intriguing in flashback. Because Leonard's mind was a puzzle, he cannot settle his memories in a forward order. So the movie was cohered by many piece of fragments, just like his mind labyrinth.
But in this obscure and recondite memory chaos, the director do give us a clear clue to follow the plot. The colored frame is flashback and the black-and-white is positive sequence.
