Well Kiasutha, you have again shown your amazing google-fu! Where/how do you find these sites? Good stuff.
Sepp:
As with most nations, I think you will find that there are/were a variety of answers to you question on French truck tarps. I can't say from any extensive personal research, but from what I have seen in pictures over some years I believe that the French sought to match the tarp to the truck, including the camo patterning. But tarps do not have anywhere near the longevity of the vehicles themselves, so in any transport unit I have ever seen (in many armies) some of the vehicles have ad hoc replacement tarps. These are often mono colored.
Also tarps fade in the weather much more quickly than the paint jobs on the vehicles. So even if they start the same, wthin just a matter of a week or two they will be "almost" matched at best. And the tops will weather faster than the sides, and some vehicles will see more sun or more rain than others, and so will have faded into different shades.
So ... my approach is to try to paint a variety of subtle differences into the tarps of my trucks. Maybe 2 or 3 similar (but not identical) colors, and then a couple of different under-coats or differing levels of dry-brushing, to make subtle differences. These last techniques (differing under-coating and dry-brushing) can work as well on camo'd tarps as monotones.
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As an example, here is a picture of my French Citroen half-tracks. I chose to paint them in an interesting French camo pattern. I also camo'd the tarps. In some cases the patterns on the tarps is continuous with the camo on the vehicles (matched tarps to trucks), but in other cases is is not continuous, nor even continuous from the tarp on the cab to the tarp on the cargo bed (mis-matched tarps to trucks). Also I have tried to weather the tarps more heavily than the vehicles themselves, and to weather the large flat top surface more than the sides.
I did this weathering all with dry-brushing. If I were to do it again, I would also vary the under-coats on some of them, and maybe even put some tan in the base-coat of the camo pattern for one or two of the tarps. I managed to get some variety, but not as much as I would have liked.
Just ideas. Your mileage may vary. Try what you like, and let us know how it works out.