As soon as you start importing in bryce , bryce asks for the separate textures. And you have to show Bryce the folders where the different textures are stored. And once imported you can select every single group( first select nothing, than hold the "Crtl" key and select with the mouse) and change color and so. So far uvmapper isnt involved, only if you want to create your own texture But look in the bryceforum for better help and there are several tuts out .