Unfortunately I don't have a chip as you have guessed.
It really is fascinating as you say. The mixes are so varied, much more than I thought they would have been before I sprayed them! I am so surprised that the two that I though can't possibly be it, 5 and 2, are the two that you say are the closest! So Dark Earth was quite a sandy colour then?
I ended up going with number 4 on my model as I thought I would just split the difference haha I will be sure to post a pic when the model is all done.
Edit: just for fun I think I will give your mix a try and see how it compares to the others.