I think navigation can be route only or track only, not both at the same time.
You can navigate a route and perhaps view the track on the map screen at the same time, seeing where it deviates from the route and using the cursor for your location and direction etc..
The way the 276CX handles this seems a bit weird.
If I create a route and navigate it (without roads), any tracks I have set to 'show on map' stay visible at whatever colours I set them to, and the route is shown as the magenta colour used by Garmin.
The nav data fields reflect this as 'Dist to Next', 'Dist to Dest' etc. match for the route.
Then while still navigating the same route, I go into Tracks, go into an individual track and select Navigate, the route disappears and the nav data fields now show the distances etc. in relation to the track.
Next, while navigating the track I selected, I re-activate the route, both the track and route show as magenta, with the route being slightly brighter, and the nav data fields reflect the route stats again, not the tracks.
Deactivate the route, the route is no longer shown and the track returns to it's normal colour