I would like to change the color of the checkmark and the background
color of the uicontrol checkbox to something other than black on
white. I am reporting on the status of several things using a
checkbox and when they are all off I would like a blank checkbox;
when they are all on, I would like to show a black checkmark on white
background and finally when some are on and some are off, I would
like to have a dark grey checkmark on a light grey background. I
need the functionality of a checkbox (user changes the status of the
box by clicking on it) but if there is something similar that would
work just as well, that is fine.

Many thanks.