I didn't found an option to change the white part of the explorer navigation.
click on "change skin colors", click on the combo box and select "show me the skin defined system colors" and change the color for "window background".
but be aware, this will change the window color everywhere.
the window text color is the color below the window background. most likely, you'll need to experiment.
and what Karen said, but I think that might be limited and not a global setting... I had to start a blind over because I changed that setting but then couldn't remember where I had done it.