Hiding the number of messages under Message List Header

In Thunderbird Config Editor, find and change toolkit.legacyUserProfileCustomizations.stylesheets to “true”. Close Thunderbird.

In your profile folder, create a folder called “chrome”, then a file named “userChrome.css”, edit the file in any editor and add the following line:

#threadPaneFolderCount { display: none !important;}

Start up Thunderbird and it should now be hidden, if not, double check the config editor setting and the other steps if still further issue.

Changing tag background and font colours

Making sure Thunderbird is closed before you do any editing. Simply add on a new line, in the same file mentioned above.

/* Change the background color of tagged messages */
/* Tag name: Important */
treechildren::-moz-tree-cell(Timportant) {
    background-color: red !important;
}
treechildren::-moz-tree-cell-text(Timportant) {
    color: #FFF !important;
}

This should turn your emails, set with the tag “Important” to have a background colour of “red” (can be changed to another colour using HEX colours). Then the font colour to #FFFFFF (white).