"The red shoe: a source of fascination, power and mystery to both its wearer and beholder." -Anna Sutton, The Australian Ballet
I was a ballet dancer as a young girl and always loved pointe shoes. One day, I saw a red pointe (toe) shoe, and my heart skipped a beat. It was the most unusually beautiful thing I had ever seen. I've been drawn to red pointe shoes ever since.
Why was the shoe so alluring and unusual? It's because red pointe shoes are rarely seen on stage.
Pointe shoes are traditionally pink. They can also be quite expensive because ballerinas go through multiple pairs per show. Because of this expense, if a red pointe shoe was needed for a show, multiple pairs would either have to be specially ordered or dyed. Ballet companies have a budget just for shoes so they have to plan for using a red shoe in a show in advance. (Thank you to my volunteer work with The Louisville Ballet for knowing these facts!)
A ballerina that wears a red shoe is usually very significant. When I see a ballerina in red pointe shoes, I pay attention. She's usually the star of the show. In the event you see a ballerina (or ballerinas) wearing red pointe shoes, it would indicate the use of symbolism in the story, kind of like Dorothy in The Wizard of Oz. (I wanted those shoes so badly after watching that movie!)
The red shoe not only is significant in ballet and in the Wizard of Oz, but it has been an important symbol in many stories throughout history. See more about the history and fascination with red shoes via this article from Anna Sutton at The Australian Ballet.