Clothes say a lot about a person, and it should be no different with characters. Albeit writers need to beware of info-dropping about clothing, or setting a character in front of a mirror just for said-character or narrator to go over ever inch of their appearance. However, little bits of description here and there about your character’s apparel can say a lot about your character, even if we are told not to judge a book by it’s cover: We do so frequently.
Clothing can give an idea of a character’s social standing or wealth. Velvet, satin, damask — these fabrics speak of wealth while wool and cotton are more common, less expensive. Throw in authentic gems and the reader knows the character is loaded. Make a character’s clothing patchy, threadbare, and the reader will know the character is poor. Of course, appearances can be very deceiving, which can lead to writerly fun when toying with readers’ perceptions and then standing them on end.
Colors can be just a telling. Perhaps your character favors certain colors or just one in particular — their favorite color. Certain colors or color palettes can also hint at personalities: yellow, a bright, warm person; pink, a bubbly person; blue, a calm person; and so on. Once again, it might be fun for a writer to play with these concepts, and have a character who by nature is a pessimist, or just plain gloomy, really enjoy the color pink and actively seek it out in clothing.
The types of clothes worn also speak volumes. A woman who wears form-fitting clothing or revealing clothing is most likely secure with her appearance or sexuality; of course, that is not always true. A woman who prefers to wear pants and t-shirts might just be a tomboy. There are also men who prefer to dress as women, and there are men for whom dressing up for special occasions is like a trip to the dentist.
Apparel can also bear sentimental values: a piece that belonged to a relative or lover, a piece found by your character, or purchased by your character on a special occasion or trip — the list goes on. Such pieces can hold character development or even plot, similar to the “Together in Paris” necklace worn by Anastasia in the Fox film. Do not discount the power mementos can hold.
Once you get a feel for what your character likes to wear and why, practice restraint — don’t go writing a paragraph of description, which will only bore your audience to tears. A sentence here or there, accompanied by character actions, will suffice.