t_standard and tdheader... with Firefox and if you have the web developer add-on..
you would simply right click on one of those 'buttons' -- Inspect Element and you could see the container classes being used..
now one issue is that t_standard and tdheader is used all over, so you'll affect other elements on other pages as well.. but that might be a good thing too, since you want it to change consistently all over
but that's where you'd start