We use fiber optics a lot in theatre, especially for starfields on curtains (called star drops). It's a pretty simple matter to embed the fiber optics in cement or plastic or whatever, but the color changing properties are somewhat difficult. At Valleyfair (the amusement park I work at in Minnesota,) we illuminate our star drops with theatrical lights that are able to change color by means of colored discs that go between the light source and the fiber bundle. But to get the amount of color variation and seperation that the Epcot panels have (at least from what I see on the pictures...it's been a year and several months since I was there last..) would be beyond that. I suppose they could just use spinning multi-colored discs instead of the single color ones that are often in those spotlights. That would be somewhat like the fiber optic trees and stuff that are starting to be sold in stores.