Interesting. The US military is field testing lightweight camoflouge tarps for vehicles and soldiers that come in different colors and textures to match different terrains and weather situations. They can even shield infra red light in order to prevent heat exhaust from being detected by infra red cameras. There is also a technology that is under developement which is similar to the cloaking technology the predator used in the predator movies. A fabric material that adapts the color of its surface to match the background effectively becoming transparent and making the wearer invisible.
I ask you, how practical would it be to paint a mech in the field to hide it when it gives off so many other tell tale signs of its presence?