I was thinking that a really good feature would be to have the option of colouring the last (choose between) 1-5 tabs. That way when you look at the screen, you know that:
red overlay = current tab
green overlay = last tab clicked
magenta overlay = tan two clicks back
Obviously you can assign any colours. Maybe a monochrome scheme might be less jarring. i.e. Red --> Pink.
Don't think this can already be done. Please let me know if it can.