No, seriously, think about this for a moment. In L. Frank Baum’s original work, what color was the Emerald City?
Your first thought will probably be ’emerald green’, and your second will probably be that there’s some kind of trick here. There is.
In the book, the Wizard didn’t know how to make a city where everything was green. So he made a city that was totally pure white, and told everyone that they had to wear green glasses to prevent the dazzling glare of the ‘green’ city from blinding them. They quite naturally saw everything as being green once they wore the colored lenses, but because they were gullible, they were taken in by the Wizard’s explanation.
Of course, making a White City is even harder than making an Emerald one. So there’s a great deal of irony in the fact that, in attempting to deceive everyone into thinking he had made a lesser accomplishment, he made a greater one. There are also many associations to be made in the real world, but that’s another story and will be told another time.
Also, the Slippers are silver. But I don’t know that they’re symbolic or emblematic of anything. If the movie makers hadn’t wanted to show off their color technology quite so much… oh well.