Back in the time of Renaissance theatre, the clothes worn by a fictional character basically determined his (there were no actual women on stage, just men playing women) personality. Like in the real world, the outfit worn caused the audience to get a certain feeling about the character. For example, a madman would be dressed in rags and strange colours, whereas a king would always wear a mantle. In fact, an actual king without his royal attire would not be viewed as a true king. In plays, this was especially important, as the audience had to work with what they saw on stage. Interiority, the difference between the inside and the outside, was not used. After all, it just would be unclear… Until Shakespeare came along.
Shakespeare’s Hamlet probably was one of the first plays playing with the characters’ outfits, especially those of Prince Hamlet himself. At first, he wears an inky cloak resembling his grief, although he claims that it does not – in fact, nothing material can describe how grief-ridden he is about his father’s death. This is not the clearest example of interiority in the play, though. It becomes even more obvious when Hamlet decides to pretend to be a madman. In order to do so, he appears disheveled in front of his family and the audience, to make them believe he is going crazy. Whether he is actually crazy or not, which might be the play’s main theme, never becomes entirely clear.
What I am trying to say is that a character’s looks basically determine how the character is viewed by the audience, whether it is a play or a book. More often than not, the choice of clothing is a public display of a character’s personality – trying to hide that personality by wearing opposing clothes still counts for this. A writer needs to think of what his or her characters’ looks say about them. Even a short description can completely change the audience’s mental image. For example, a girl in a black leather jacket might come across as a biker at first glance, right up until the moment she puts a flower in her hair. Characters should be like real people; not black and white, not even shades of grey, but colourful.