@organicmaps @crowdotblack @ai6yr
Hmmm... I might not be sure of your question.

The 2-tone trails that GISsurfer can display is one set of trail data that is displayed twice.

If there is a second set of GIS trail data then that data could also be displayed twice. Perhaps with a wide orange line and then a narrow black line.

The purpose of the 2-tone approach is so the trail is easy to see irrespective of whatever data the basemap is showing.