Hi,
I think this might be a small and basic feature yet a significant one. Garmin helps us capture lot of details about our activities, but sometimes what we really want is to know during my activity did I feel good, or how good was my recovery.
Color coding an activity green, yellow or red based on how good or bad they went, would give me a very good high level understanding of how well I am training. This could be implemented in the calendar section as well.
Thanks,
Athar :)