Uhm, I believe what you want is an extension named Colourful Tabs? Get it from here: https://addons.mozilla.org/de/firefox/addon/colorfultabs/

Also, if you can and this doesn't help, please write in English.

Thanks!

I don't mean that.Thanks anyway! My problem is that, I found it difficult to distinguish which tab were the tab I'd browsed and should be closed.

Maybe something like this? https://addons.mozilla.org/en-us/firefox/addon/aging-tabs/

Now I think I've got the reason for confused : the color of active tab is different to the navigator toolbar.

like this :

I'm locking this thread because you also created a thread in English about this issue.

Locking duplicate thread.
Please continue here: [/questions/933610]