Quit the game, restarted and reloaded the same game, and now it looks like this:

BTW, I updated my NVidia driver yesterday, I'm on 347.25, which NVidia GeForce Experience says is the most current.

I have experienced the exact same problem with a trade route.

Lucky Jack reported in reply #2 above that he had opened ticket #RAY-899-87620 for this problem.  Do you need another ticket reporting the same problem?

I've opened ticket #PPJ-131-20782.

I'm not having much success reproducing the vivid trade routes found in my original posts.  However, it does seem easy to reproduce a nearly invisible trade route.

I started a new game with the .71.1 opt-in beta, and after establishing my first trade route it looked like this:

After saving and reloading, the trade route is nearly invisible:

It's black, not blue like it was originally, so it can't be seen on the black space background, I had to highlight it a little further out where it could be (poorly) seen against the gray background.

I'll see if I can update the ticket with my latest saved game.

I am getting this issue as reported in the OP. I see that support responded to the ticket. Is it on a list to be fixed?

Still happening in Beta 5.