To add, it stays light blue on the most zoomed in setting then goes between light blue/default red on the zoomed out options.

So, I set navigation: road colour to light blue and navigation: arrow colour to white in the def file. In game, the route advisor correctly displays the new colours but when the world map is open, the colour of the GPS route flickers between red and light blue. Did I do something wrong during instal...

Pictures explain it all. Near Stockholm. Was coming from port, left at the roundabout and right out of the tunnel down the slip road. Fell through just after the slip road, as seen on my marker on the map.