One thing I've noticed is the structure of the GPX file affects this. I don't recall having problems prior to 1.52.
Repro in 1.52:
0. GPS= Garmin 12XL
1. Download new GPS track log to TopoFusion. TF draws trail black.
2. Look at .GPX file. Each point is in it's own (trkseg) element.
3. Using a text editor, strip out all the extra trkseg /trkseg tags.
4. Restart TF, it now renders trail in the correct color.
Does TF have any heuristics in finding breaks in the track log, such as looking at times or unexpected gaps in the time or distance? Since the 12XL stores only 1024 points, I often stop and restart the track log to get only the trails sections I need. Could this affect the additional trkseg tags?