ComboBoxStyle : how to style the editor

Using ComboBoxStyle to style the ComboBox control, you may override the background and the label.
But if the ComboBox is made editable you can't style the editor.
The "__editor" variable of ComboBoxStyle is marked as internal, and by the doesn't give access to text color of the editor for example.
Further, the mouse area of the editor does not seeem to correspond to the "__editor" item being painted.