I am so gutted.
I have been looking for years for a way to highlight unread and manually mark tabs I want to return to.
This does it perfectly in a clean profile - but conflicts with Tree Tabs, which I cannot do without!

My userchrome.css:
=========
/* comment, new lines only, can span multiple lines
This code used by Unread Tabs Restorer addon - which changes the title when loading, causing it to be red font, until the tab is selected.
♥ MANUAL CHANGE TAB COLOUR BY RELOADING TAB WHEN UNSELECTED ♥
! CHANGE about:config toolkit.legacyUserProfileCustomizations.stylesheets = TRUE (enables this css file to work)
*/

/* unloaded tab blue (not used):
.tabbrowser-tab[pending] { color: blue !important; }
*/

/* loading tab grey (not used):
.tabbrowser-tab[busy] { color: dimgray !important; }
*/

/* loaded unread tab is red -after Unread Tabs Restorer changes the title
- persists when tab is unloaded
- doesnt persist through sessions
- colour disappears when tab is activated
*/
.tabbrowser-tab[titlechanged] { color: red !important; }

Works for me and doesn't conflict with other extensions that change the tab title. Thank you.

Great add-on for good ol' Fx lovers

works great. added css code to my userchrome.css file and unread tabs are styled accordingly. Very happy. This extension adds alll three styles....was using my own user script inject via fx-autoconfig but just stopped working and this is easier and works just as good. Score! Thankss

Exactly what i was missing, works perfectly with PAXMOD (Tabs in multiple rows).
Thanks a lot, well done :-)

ps
how to make the tab title bold or italic?

Does exactly what it says it does. Absolutely no complaints.