alternating drawer background

I find it difficult to look at the multiple levels of drawers I’ve got. I’ve been able to identify the CSS I’ve got put into inline CSS, but how do set the background colour in an alternating fashion so it’s easier to discern which drawers belong to which rows?

I should say that all the drawers are based on the same table with a field called “Tabs” to specify which level it belongs to. (This table is an unmanaged appexchange object)