If you have tried Galeon you know what i'm talking about, when you tell a
browser tab in galeon to load a page, the text of the tab becomes red and
turns normal color when the page is loaded. If you switch away from the tab
before it has finished loading the tab will become blue when the page is
finished loading, indicating that the page is done loading but you have not
yet seen it.

Hope this is relatively clear.

This could be useful when IRC'ing, monitoring a log file or someting like
that. When a not-focused tab has new output written to it, the tab changes
to another color (gtk-theme marking color perhaps?) until it is chosen by
the user, where it changes back to normal color.