Changing Background Color Of Multiple Select

I have two multiple select inputs. Initially the first contains a bunch of
items and the second is empty. Using a common method, I move items back and
forth by double clicking on them.

This portion works perfectly, but I would also like to change the background
color of the select element with the current focus. I have defined the following classes:

..selected {
background: #C0FFFF
}
..deselected {
background: #FFFFFF
}

Using the following function below I am able to shift the background color
of rows containing content, but the color of the empty rows remain the
"selected" color. How can this effect be achieved for all rows, whether they
contain content or not?