Hey Henry: make a 1000x1000 TIF/JPG image with (small scale) camouflage tints (greens/autumn oranges...). Open TG, make a camera, have it point down (-90/0/0) and hover it above your trees at 200-1000m. Attach this to the imported image file (which should repeat both ways). Call the image shader something. Then open up your tree object, attach a surface layer between the default and the under that. Rightclick on colour, and add the named image shader as the colour (or even luminosity for some interesting results). Then play with the quantity, height of the camera, etc. I use this method to offset the uniformity/uniformness of a single pop (or multiple pops, of course). Works very well.
---Dune