Configure the option "Cell marker: Color" (set the color; File | Options)

Here you can configure the color that PlanMaker uses to paint the border around the active cell. Note that you must also set the option to use a user-defined color.

CellMarkerColor

Registry Hive	HKEY_LOCAL_MACHINE or HKEY_CURRENT_USER
Registry Path	SOFTWARE\Policies\SoftMaker\PlanMaker 2018
Value Name	CellMarkerColor
Value Type	REG_DWORD
Default Value	80000
Min Value	0
Max Value	16777215