Are you really bored with the same colour of all the tabs in your firefox browser? Then its time you need to change the colours of the tabs isnt it? But there are no inbuilt options in firefox which can help you with this. You need to install a Firefox Add-on called as ColourfulTabs which changes the colours of the tabs automatically even if they are active or not.

The currently activated Tab is of fixed colour and the unselected/unused tabs will be faded to make sure they dont disturb you, while you are at some serious work using firefox browser.

Download Link : ColourTabs