List component, transparent background

Anyone know what CSS declaration to use to make the background of a LIST component transparent?

I’ve tried using the following:

_root.myList.setStyle("backgroundColor", "transparent");
_root.myList.setStyle("backgroundColor", transparent);

Somewhere on some Google search result page I also got a hint that this could be used too:

_root.myList.setStyle("backgroundColor", undefined);

But none of this works. I know the same style declaration works on all other components like TextArea and all, but it doesn’t seem to work on the List. Any ideas, please?