I think I'll probably go with the first description. It's interesting that Baum's descriptions of the city doesn't stay consistent throughout his many books.
For instance in the original Wizard of Oz he describes the city as being green on the outside but white on the inside (hence the green glasses the Wizard forces the inhabitants to wear). But the glasses are nowhere to be seen in the later books. He then describes Oz as being gold plated with green merely the dominant color.
Eventually the whole green thing disappears altogether, as the buildings are decorated with not just emeralds, but sapphires, diamonds, and rubies.
So much for the "Emerald" city!
"No matter how many times my artistic ability fails, I always want to try again." - Anonymous