In the original novel, Dorothy's slippers were silver.
L. Frank Baum's 1900 book, The Wonderful Wizard of Oz, calls them the Silver Shoes. They originally belonged to the Wicked Witch of the East, whose death beneath Dorothy's farmhouse transfers ownership to Dorothy. The Good Witch of the North tells Dorothy that the shoes possess an unknown charm.
Their most important power is revealed near the end of the story. After defeating the Wicked Witch of the West, Dorothy learns from Glinda that the shoes can carry their wearer wherever they wish to go. Dorothy taps the heels together and reaches Kansas, but the shoes fall off during the journey and are lost in the Deadly Desert.
The famous color mix-up comes from the 1939 MGM film, which changed the shoes to ruby red. The change showcased Technicolor's vivid colors, especially when Dorothy entered Oz.