When Curley's wife appears in the barn where Lennie is sitting and thinking about the consequences of the puppy's death, she is wearing mules decorated with red ostrich feathers. These shoes would not have come cheap, because ostrich feathers in that part of the world would have been expensive and difficult to come by. Ostrich feathers would have made the shoes look particularly glamorous.
These shoes therefore reinforce the socioeconomic and cultural divides between Lennie and Curley's wife. Thanks to her marriage to Curley, she has access to resources and luxuries that Lennie is unlikely to ever have.
The shoes also seem to fit with Curley's wife's reputation of being flirtatious. These shoes were clearly designed to make herself stand out and be noticed.