I think that the white is still too white. Even marble chips have trouble staying that clean. I suspect that making the gravel a little lighter than the natural dirt will go a long way. Perhaps a white specked texture over a base that is between the current white and the natural earth.

A quick check of google images show gravel roads to be more of a medium grey for the most part.
A new crushed shell road would be that white, just not too durable.

Good luck.
So far it is looking good.