In the CustomListView class module there is a class Global 'dividerHeight'
In the Initialize Sub for the downloaded example it is set to 2dip .. Change it to 1dip.
The border color is also set here by changing the ScrollView's (sv) color
B4X:
Public Sub Initialize (vCallback As Object, vEventName As String)
sv.Initialize2(0, "sv")
items.Initialize
panels.Initialize
dividerHeight = 2dip '@@@ Change to 1dip
EventName = vEventName
CallBack = vCallback
sv.Color = Colors.Red '@@@ this sets the dividers color