What colour were dorothys slipers?

Dorothy's slippers in "The Wizard of Oz" are famously ruby red in the 1939 film adaptation. However, in L. Frank Baum's original book, "The Wonderful Wizard of Oz," they are described as silver. The change to ruby red was made for the film to take advantage of Technicolor, creating a striking visual element in contrast to the black-and-white scenes at the beginning.