After upgrading to BC19, I noticed that some user permission sets are highlighted in red.
Checking on the code reveals that Microsoft added new Style and StyleExpr on the field.
The permission sets are highlighted in red because the related permission set is no longer exist. One of the reason is because the app that installed them has been uninstalled or the installed app no longer have that permission set.
You also get notification when you open the User card that you can safely delete the red permission is no longer exists. It’s a nice little touch from BC19 update.