Changing the value of <route_color> in settings.xml (or default_settings.xml) makes no difference for me. It is not even the default value that is rendered (9903FB), but instead some semi-transparent pale yellowish colour, which is almost invisible.
Changing e.g. the <arrow_color> works well.
What is going on? How can I change the colour of the route? It is useless as I cannot see the route on any primary road (rendered yellow) and it is barely visible on any other. :-(