It's hard to see from this picture, but I added the next bit of stitching to my trunks. See here for how it looked before adding this pass. I used Connecting Threads "Essentials" cotton thread in grey. I love this thread for general sewing - it is smooth and long staple so there's not much lint, and it is a nice thickness. Not as heavy as Mettler 50 wt cotton but not as thin as Aurofil 60 wt 2 ply. I've used both of those for piecing, but now prefer the Essentials.
At a distance, it doesn't look a great deal different in color than the first thread, but on closer inspection, one can see that it is lighter. It adds the subtle shading, the darker underneath where the lighter bark has pealed off. See here for reference to the real thing.