It’s a category not really a group. People can set preferences and “watch” a category in their email preferences but that’s not really the same thing as being a member.
There IS a groups ability, too, but that would mean Ring Makers have to actively manage group membership. We may want to do that to show Wallet Ring members, AND you can @-mention groups which notifies all the users. This probably needs a tracking Github issue if we want to go this direction.
Yes, colours are possible.