As I've posted in this thread, by 6164314, the navigation line in my watch changed sometime in the middle of Sept. to a much thinner one that I've trouble seeing with most of my maps: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-6-series/194034/how-to-change-the-colour-of-the-navigation-line
Contacted support, but they didn't have an answer.
I started to test what possibilities with the map theme files and found out that this style field="MPM_ACTV_CRS_CLR" is used for the navigation line.
If you create different map theme files with different colours, you can even change the colour while running depending on the map background.
Create a text file and save with extension 'kmtf' to the map theme folder on watch.
This text give you a dark green line with dark green borders.
<?xml version="1.0" encoding="UTF-8"?> <garmin_map_theme> <metadata> <title>DarkGreen</title> <description>DarkGreen</description> </metadata> <stylelist> <style field="MPM_ACTV_CRS_CLR"> <color> <primary day="#ff006400" night="#ff006400"/> <secondary day="#ff006400" night="#ff006400"/> </color> </style> </stylelist> </garmin_map_theme>
Great color code page: http://www.farb-tabelle.de/en/table-of-color.htm
Some examples: Blue, green, magenta and the last-right one are red with blue borders.
The two bottom-left is the thin original that shows up if no theme is used.