I had a gs shot with a tread mill, was going to paint it, but I figured with the motion blur from the running it would be bad news, so we kept it black, with the actor wearing black shoes and pants, and it worked much better with a little bit of roto. but if you have to paint it, take the tread off, spray paint it, let it dry fully then put it back together, if you try to paint it witht he tread on, it will cause it to stick, also do not paint the undersite of the tread, nor the wood plank it slides against.