The outputDirectory is relative to the folder you're currently processing. When you're in init.bsh, you haven't started processing any folders, not even the top level. There is only rootOutputDirectory. It has always been like this.
If you're generating SVG files, you don't actually want different colors at different folder levels, do you? Don't you want just one color for the entire album? So just generate it once, from init.bsh.
I don't know why you're even discussing slidePage.js. What does that have to do with changing the colors of an SVG icon?