Be able to change your rider dot colour during a group ride if needing a sweep or if leaving the ride. It can be hard for the sweep to tell who is leaving or who needs help. Maybe a “cool down” button would work
Color is based on Cat, unless otherwise set by ZHQ for special events.
Reality is; most people won’t do what you’re talking about; it’s rare enough to actually get most folks to reply if they even need a sweep, and even then, they might not say anything until it’s beyond way too late.
Then comes the even larger issue.
We can’t see over 100 riders; so a changing dot color is rather meaningless if the ride is over 100 riders, and they aren’t visible on the map anyway.