Generally with an obj that's been created in a model creating app it will be exported with an mtl file embedded. It's the mtl file that assigns the colours and textures to the polygon groups as determined by the author. With TG2 you sometimes have to ensure the mtl file has imported correctly along with any texture images. And other times you have to import your obj file into a 3rd party app such as Pose Ray, or Blacksmith 3d, and then re-export it to set up the obj file with its mtl file so that it imports correctly into TG2. I believe the Planetside staff are aware of this obj/mtl importing glitch and are working on it. Please correct me, anyone, if I've got that wrong.
John