Of course, you can blend the painted shader(shown here), or image map, by a fractal itself, giving fractal coverage of the secondary colours over the entire population. Set the imagemap/paint shader as a child to a surface layer(apply colour = unchecked) and use a fractal blender on that.
You also have the slope/altitude constraints from the surface layer to play with...
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.tgd requires Mr_L's 'Bush_01a.tgo', but will work in any other object with the same setup
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