Once the time has come for the bookmark notification to appear, the notification icon and its colour are similar to the one used for message notification. It would be much more clear that “that’s a bookmark notification” if it was placed somewhere else near the profile picture. (new position: bottom left, for instance). It would also help if the colour was different from the existing one for PMs.
Here you see 2 green notifications, but you cannot tell if it is a bookmark or message one.
I consider messages to myself as important as messages from others. Current behavior works for me. 
This is very much by design.
Green notifications now mean “high priority notifications”. A bookmark reminder is high priority, A PM is high priority, having a topic assigned to you is high priority.
Adding another color here is not on the table. A per user setting for “my bookmark reminders are not that important” is also not really on the table.
I agree that reminders are very important. I just receive many PM notifications daily and it’s hard to know which one is a reminder and which one is a message, without opening my profile. But I see what you mean and makes sense now. 