The new feature phab:T94634 ("Quieter Echo notifications for Flow posts") was released this week. This will change the red New Notifications badge to grey, as soon as we click on it, whilst retaining the number for any still unseen Flow notifications. The goal is to help make it clearer when we get a brand new notification, if we had previously decided to leave some unread - E.g. If I had unread notifications, but wanted to leave 2 of them for later, the badge will be colored grey, and have the number "2"; then, when I receive a new notification, I can easily see that by the fresh red coloring as well as the number incrementing, without having to recall what the previous number was.
Design tweaks to fix the low-accessibility of the white text on grey background, will follow. (phab:T98526)
Note: There is one existing bug for this - it currently always shows as grey if we have "1" unread/unseen notification. That bug has a patch awaiting code-review and will be cherry-picked as soon as possible. (Technical details at phab:T94634#1264132)