To fully explore this concept, I have to go into important plot details of Midnight in Paris. If you have not watched the film yet, read on at your own risk. Woody Allen's Midnight in Paris (full review) is a sweet tale of nostalgia. Gil, an American writer in 2010 visiting France, finds a way to travel back to 1920s Paris. He has literary and philosophical discussions with all his idols (Hemingway, Stein, Dali, the Fitzgeralds) while falling for a well-known mistress of the salon crowd. He tries to balance these new stimuli with his engagement to a wealthy entitled woman.
Like many of Allen's films, the setting becomes a major character in the film. He hits on famous locations in four distinct time periods for comedic effect and allows the historical allure of Paris to define how Gil relates to his own life and experience. More important, however, is the use of light.
Midnight in Paris is a very yellow film. Seemingly every added light source has a yellow filter on it to brighten, highlight, or distract from the action happening on screen.
In the present, Gil's worldview is blinded by the distractions his future in-laws and fiance bring. The plush hotel is difficult to look at, the furniture shops meld into a pool of yellowed wood, and every restaurant blurs beyond his immediate surroundings.
As soon as he travels back to 1920s Paris, the contrast of the night and the magic of the culture make the yellow seem intimate. It is the flicker of a well-placed candle or the glint of an abundance of amber liquor at a party. It's a celebration of everything Gil ever aspired to be. He is able to breathe and take his time at night in the distant past, where following strangers to a party was a possibility and pausing for a drink with everyone was a necessity. He can clear his mind and grow as a writer.
When the film jumps into a further past (1890s Paris), the world is overrun not with yellow but gold. While Gil thought 1920s Paris was the golden age, his fellow-traveler may have been correct in labeling the age of Gauguin as the true golden period. Everything is alive in a warm glow of amber. The world moves slower but the beauty is undeniable. To Gil, who suddenly realizes his time-traveling is not a sustainable lifestyle, the 1890s are an illusion that will fade under the daily struggles of life. His companion's departure into the golden blur of a can-can nightclub only act as further evidence of his belief. Staying in the 1920s will make him long for a different unreachable era rather than force him to develop an identity in his own time.
The big punchline of the film--the detective lost forever in time--confirms this theory. He winds up at Versailles, a palace coated in gold, that is displayed in cold white light. Everything is dull and drab because the detective has no interest in visiting the past. He was fulfilled in the present and now he is lost forever to a nostalgia that has no effect on him.
A huge draw for Midnight in Paris is the Modernist nostalgia. There is a large audience of people who look up to Hemingway, Faulkner, Fitzgerald, Joyce, and all those experimental writers and artists of the time. They produced something that still feels new and special but would be seemingly commercially unviable in the modern world. However, nostalgia alone does not create a strong film.
There are people who dismiss Midnight in Paris as sentimental fluff not worthy of discussion. I believe the technical design of the film, such as the lighting design, offers a variety of ways of reading Allen's intentions in the film.