Quite clearly this question relates to the way in which clothing is used by the narrator to give us key clues about character and the way that attire is a key indicator of the kind of person that wears it. You will obviously want to focus on the descriptions that the narrator gives us of the key characters and link those to their actions to support your thesis. A suitable thesis statement therefore might be as follows:
In "The Bride Comes to Yellow Sky," Crane uses clothing to reveal key aspects of character.
This will give you a focused statement that you can use to explore maybe three characters and their clothing, relating it to what they say and do. Certainly the "maroon-coloured flannel shirt" of Scratchy is an excellent example of the way in which his virulent fashion sense corresponds with his virulent character!