* Modifying the appearance: You can paint the horse in colors typically associated with a different gender, or add accessories like saddles or bridles that are usually associated with one gender or another.
* Giving the horse a new name: You can choose a name that is typically associated with a different gender than the horse's original mold.
* Creating a backstory for the horse: You can imagine a story for the horse where its gender is different from what it is depicted as in the original mold.
Remember, these are just ways to play with the idea of gender and your own perception of the horse. Ultimately, a Breyer horse's gender is a matter of your own imagination and how you choose to interact with it.