Just take a can of paint and have it drip out the back of a car and drive up and down a dirt road every few hours for a week with other cars using that road and you will see the road spoted everywhere with that paint in a week. Now try and hide something like a IED in the road or on the side of it buried and see if you can not easily see such a thing. Now take a few cars and do the same thing with diffrent colors and over time changing colors to new diffrent ones giving the road diffrent aged layers of painted spots that would be almost impossible to paint by a human to match any area that has been dug up.
If you had even just 1 out of 20 army trucks, tanks, transports having a device that droped paint balls about 1 per 1/10 of a mile it would create a painted spoted landscape covering everything. Having paintballs or paint that is wet that gets tracked by people, and cars will cover a large area with tiny spots of paint that will dry all over the place. Using diffrent colors and how much you use will create a painted spoted road that a Human trying to paint to match any area that is dug up or disturbed would be very difficult at best.
Ever see paint spilled out of a moving car that has dried all over the road? Notice how the paint is spread and spoted everywhere from such a accident? Even a little paint will be tracked and spread of a large distance even very far from the paint spill itself.
You can have a paint gun even shoot paint balls every so often into the air that would fall to the ground and splat to be tracked by anything touching it.
Using paints that show beter or only with night vision or other army optical gear would make it hard for anybody to dig or place a device into a road with out the road showing the paint spoted pattern as diffrent.
And over time the diffrent paints and amounts used that will be randomly changed would make it very hard to match a pattern that time has had many diffrent ages of faded and colors and even diffrent use would create.
Just take a can of paint and have it drip out the back of a car and drive up and down a dirt road every few hours for a week with other cars using that road and you will see the road spoted everywhere with that paint in a week. Now try and hide something like a IED in the road or on the side of it buried and see if you can not easily see such a thing.