There are 3 bars, but I cannot remember off the top of my head which colors are which (I don't have DirectSOFT installed at home)
One is whether the rung has been edited but not compiled
One is whether the rung has been edited/compiled but not saved to disk
One is whether the rung has been edited/compiled but not saved to the PLC
If there are no bars, either it has not been edited
OR it's been edited, compiled, written to disk/PLC.