How do I to color TB folders and thread where are present new messages?

You must add those code row into file userchrome.css:

/* ----- font red color - new mail in the left (accounts) pane --- */
    treechildren:-moz-tree-cell-text(folderNameCol, newMessages-true) {
color: red !important; /* red  */ }
 
/* ---- to make the account name in a colour when new messages arrive --- */
    treechildren::-moz-tree-cell-text(folderNameCol, biffState-NewMail,
isServer-true),
    treechildren::-moz-tree-cell-text(folderNameCol, specialFolder-Inbox,
newMessages-true) { font-weight: bold !important; color: red !important;
/* red */ }
 
/* ------- has new unread messages ----- */
    treechildren::-moz-tree-cell-text(container, closed, hasUnread, read) {
text-decoration: underline; color: red !important; /* red */ }
 
/* Change the color of containing folders */
treechildren::-moz-tree-cell-text(hasUnreadMessages-true)    {color: blue
!important;} 

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