Thunderbird: Making a folder with new messages stand out

On Thunderbird 3.0.7, this little extra file turned the folder names with new mail red and bold:

(the “chrome” directory needs to be created)

$ cat ~/.thunderbird/sdf2k45i.default/chrome/userChrome.css
@namespace
url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

/* Setting the color of folders containing new messages to red */

treechildren::-moz-tree-cell-text(folderNameCol, newMessages-true) {
 font-weight: bold;
 color: red !important;
}