......... Garmin Colorado has a magnetic compass built in, so it can show heading......
Surely .... it can only show a heading relative to its own fore and aft axis, can it not ? If it isn't bolted along the fore and aft axis of the aircraft it won't show the aircraft heading, only the track made good.
Of course, it could have compass needle, which would point to magnetic North, but that's not the same.
Educate me.