See more from fenix6 threads: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-6-series/204247/how-to-change-the-colour-of-navigation-course-follow-line-with-your-own-map-theme/ or https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-6-series/271472/how-to-turn-off-a-virtual-partner-while-following-a-course/
It's also possible to change the color of the direction arrows with your own map theme. It's probably possible to do them transparent and not visible too, but this was just a quick test that I've been thinking about doing since the direction arrows were introduced.
Example with green and orange arrows with an orange line with black borders.
Example with green directional arrows
<?xml version="1.0" encoding="UTF-8"?>
<garmin_map_theme>
<metadata>
<title>OrangeTransBackGreenArrw</title>
<description>OrangeTransBackGreenArrw</description>
</metadata>
<stylelist>
<style field="MPM_ACTV_CRS_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00"/>
<secondary day="#ff000000" night="#ff000000"/></color></style>
<style field="MPM_VEHICLE_CLR"><color>
<primary day="#ff0000ff" night="#ff0000ff" />
<secondary day="#ff0000ff" night="#ff0000ff" /></color></style>
<style field="MPM_VEHICLE_BRDR_CLR"><color>
<primary day="#ff000000" night="#ff000000" />
<secondary day="#00ffffff" night="#00ffffff" /></color></style>
<style field="MPM_VEHICLE_LEFT_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00" />
<secondary day="#00ffffff" night="#00ffffff" /></color></style>
<style field="MPM_VEHICLE_RGHT_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00" />
<secondary day="#00ffffff" night="#00ffffff" /></color></style>
<style field="MPM_VEHICLE_BACK_CLR"><color>
<primary day="#ff0000ff" night="#ff0000ff" />
<secondary day="#00ffffff" night="#00ffffff" /></color></style>
<style field="MPM_VP_VHCL_CLR"><color>
<primary day="#ff0000FF" night="#ffff8c00"/>
<secondary day="#ffFF0000" night="#ffff8c00"/></color></style>
<style field="MPM_VP_VHCL_BRDR_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00"/>
<secondary day="#ffff8c00" night="#ffff8c00"/></color></style>
<style field="MPM_VP_VHCL_LEFT_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00"/>
<secondary day="#ffff8c00" night="#ffff8c00"/></color></style>
<style field="MPM_VP_VHCL_RGHT_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00"/>
<secondary day="#ffff8c00" night="#ffff8c00"/></color></style>
<style field="MPM_VP_VHCL_BACK_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00"/>
<secondary day="#ffff8c00" night="#ffff8c00"/></color></style>
<style field="MPM_RTE_ARRW_CLR"><color>
<primary day="#ff006400" night="#ff006400"/>
<secondary day="#ff006400" night="#ff006400"/></color></style>
<style field="MPM_RTE_ARRW_OTLN_CLR"><color>
<primary day="#ffff8c00" night="#ffff8c00"/>
<secondary day="#ff000000" night="#ff000000"/></color></style>
</stylelist>
</garmin_map_theme>