3D Layer import the obj file grey

It might help to explain where you got it from and how it looks textured. That said, the details in the 3D palette suggest that each of the cubes is just a lump of polygons without further sub-groups, so coloring and texturing it would be nearly impossible. This would need to be prepared in a 3D program and split up into it's individual objects.

Mylenium

It looks like there are no textures attached to the model, hence why it's completely grey. (This is usually the standard color for untextured 3D models).