Designing clothes and costumes for film is no easy task. Costumes for a period piece have to be designed to look as realistic and authentic as possible, and costumes from fictional universes (such as Star Wars or Middle Earth) have to be designed from the ground up with their own unique sets of designs and cultural meanings. However, costumes in film can also help tell a story through design and color. One of the best examples of story telling through costuming I can think of is that of Captain America throughout the Marvel films.
Captain America is a hero that's meant to embody the virtues of America itself (the idealized version to be honest). He stands for freedom, justice, and the good of all people. That's why his uniform in World War II is the red, white, and blue of the American flag; complete with a white star on the chest and an "A" for America on his helmet. Steve Rogers embodies the virtues of basic human decency and fighting for freedom. He takes these virtues from the 1940s with him to the modern day and they clash with our morally gray modern understanding of the world.
When Steve goes to work for S.H.I.E.L.D. (the shadowy government organization that often goes above the law and achieves its goals by sidestepping certain civil liberties) his suit is a single color, dark blue, and his shield has had its color removed leaving it a simple silver. It symbolizes S.H.I.E.L.D. attempting to remove those steadfast virtues from Captain America and replace them with the sterilized and cold efficiency of a shady organization. However, it's revealed that (spoilers) Hydra, the Nazi organization Cap fought in WWII, have been infiltrating S.H.I.E.L.D. throughout the decades and using it to eventually create an authoritarian state. Upon this realization Cap abandons the blue suit in favor of his classic red, white, and blue suit from WWII. This symbolizes Cap returning to those ideas of justice and freedom and using it to rally people to fight these modern day Nazis.
This same concept is revisited during the later Marvel films. After a debate on super hero law enforcement resulted in a Civil War between the members of the Avengers, which resulted in Cap and his followers going on the run, Steve abandons his shield. We see him in later films, his uniform is dirty and slightly torn; the star has also been removed and Steve is rocking a beard. Steve resembles a fugitive, underground and on the run, but more importantly Steve's damaged and dirty suit symbolizes the harm done to the Avengers and Captain America as a result of the Civil War, the symbols he once embodied have now been tarnished. Only when Cap and Iron Man put their differences aside for the greater good does Steve take up the shield and his proper uniform again.
Costuming is often an overlooked aspect among moviegoers. It is also often under utilized by film makers as a useful way to convey themes and ideas without using dialog. A lot of thought goes into the best examples of this, often theorizing what a certain color conveys or what the design/presentation of the outfit says about the character wearing it. The wardrobe department deserves credit not just as costume designers, but story tellers as well.