Okay, so in the original the Wizard of Oz, the Wicked Witch of the East (the one who's Dorothy's house fell on) wore silver shoes instead of ruby slippers. They changed it in the movie so they'd take advantage of the new Technicolor technology at the time.
In the musical #Wicked they showed that the shoes were originally diamond-jeweled, but the Witch of the East couldn't walk, and the Witch of the West her sister cast a spell on her shoes so she could walk, turning it red in the process.