I've looked at it from every direction, and your triangulation around the curbs etc (which is where you are pointing in the first two imags you posted) is 100% perfect. I've atteched another image where you can see the color differences, but like I said before, i think it's just a light/shadow thing.
The main rule for anything in Civil 3D is that if it looks good- if it looks like curb, if you quick profile it and it looks right- that it is right. Unless you have to render it (do you?) I think you are 100% good here.
This is an amazing corridor model, by the way.