Интерфейс ListCellRenderer<E>

class MyCellRenderer extends JLabel implements ListCellRenderer<Object> {
    public MyCellRenderer() {
        setOpaque(true);
    }

    public Component getListCellRendererComponent(JList<?> list,
                                                  Object value,
                                                  int index,
                                                  boolean isSelected,
                                                  boolean cellHasFocus) {

        setText(value.toString());

        Color background;
        Color foreground;

        // check if this cell represents the current DnD drop location
        JList.DropLocation dropLocation = list.getDropLocation();
        if (dropLocation != null
                && !dropLocation.isInsert()
                && dropLocation.getIndex() == index) {

            background = Color.BLUE;
            foreground = Color.WHITE;

        // check if this cell is selected
        } else if (isSelected) {
            background = Color.RED;
            foreground = Color.WHITE;

        // unselected, and not the DnD drop location
        } else {
            background = Color.WHITE;
            foreground = Color.BLACK;
        };

        setBackground(background);
        setForeground(foreground);

        return this;
    }
}