Colours on the route map on Activity app

As referenced in my previous reply, Apple advises that the line colours on your route map indicate your pace, with green being the fastest and red being the slowest:

End and review your workout

I agree with the speed theory. On a recent outdoor cycle, the red exactly corresponds to my slowest speed. My start and finish, my turnaround, and crossing a bumpy wooden bridge.

At first I assumed it was heart rate but it made no sense for the above points in my ride. I always cross the bridge slower than 5mph.

Well that does seem like an obvious answer, testing doesn't support it. It appears to reflect the heart rate ranges with red in cardio (not dangerous), yellow in fat burning, green in low. But this observation is also subjective. All this mystery could be solved with the App developer simply telling us.

Hi

The line colour reflects your speed (green being fastest, red being slowest).