you can use the property "cell background color". See the attached example.
What I understand is that you need to change line separation (between rows) color, don't you ?
In the menu, select "View > Tool palette" and then, select the paintbrush tool (I mean : click on the foreground box color, and select the color you want to use). Then, click with the paintbrush tool on line separation.
I do not know if this is Rube G code. But anyway take a lock at it
Edit: Oops to late 😉
Thanks all for the attention
Yours examples helped me