I did not have any lavender paint...no, really...if I was building a genuine salvage truck to be used under such conditions it would look much like the model does, color included. Flat black is a color that intimidates most people, a useful thing in a lawless world when you might be carrying a valuable commodity that some would be willing to take away from you. It also blends well with its surroundings in most places, surprisingly enough.
It was the latter, Model Masters raw umber thinned down about 60/40 or so and applied with a double action airbrush (which I am still getting used to). I have never tried pigments, don't know how to work with them. They are not available in my area but one day I'll have to mail order some as I have seen them used to splendid effect.
The road? Once the pan (base) was cut, assembled, and stained I got a bag of dry sheetrock compound that hardens in 45 minutes, about eight bucks for 25 lbs. Mixed it and sloshed it in, then took a piece of 1x3 and screeded (like leveling concrete) the mix from one end to the other. I did not fix the rough spots as I felt they would add character and variation in the surface.
When dry, a couple of coats of Floquil concrete paint were airbrushed on, deliberatly uneven. Did a bit more with a brush here and there to deepen the color in spots. Once this was dry, the lines were taped off and sprayed. Once that dried, some MM flat black was thinned about 50/50 and airbrushed to simulate the ground in rubber and other mung you'll see on concrete highways where tires contact. A few shots of the thinned raw umber described above and that's all there was to it. Very quick and easy. Hope this helps you out, feel free to ask if I have not been clear.