In the book they were silver.
Ruby RED Slippers.
And it was the Lollipop Guild.
Yeah, but that wouldn't have been nearly as good for showing off that nifty technicolor stuff!
By the way, has any Pink Floyd fans ever tried the "Dark Side of Oz" where you play the Dark Side of the Moon as an essential soundtrack to the movie. Pretty cool. There is debate over whether it was intentional. I think it likely was. Floyd had done some soundtracks to movies before Dark Side.