Thunderbird userChrome - change sub folder and parent folder color with unread messages?

I have the following in my Thunderbird userChrome.css file:

treechildren::-moz-tree-cell-text(subfoldersHaveUnreadMessages-true) {
  color: blue !important;
}
treechildren::-moz-tree-cell-text(hasUnreadMessages-true) {
  color: blue !important;
}

It causes folders with Unread Messages to be blue, and also their parent folders to be blue as well.

The problem is, that when I have read all the messages in the folder (no more unread messages), the current folder turns back to normal (black), but the parent folders remain blue. You can change them back to black if you hover the mouse over them, but shouldn't they turn back black by themselves?

I am using Thunderbird v9.0.1

Solution 1:

Would it not be possible for you to manually specify the parent folders to become black once the current folder has no more unread messages? Example:

treechildren::-moz-tree-cell-text(subfoldersHaveUnreadMessages-false) {
  color: black !important;
}