This is how I do it.
I set the repeating group background as “None”.
Then I create a group (not repeating) in the repeating group´s cell and set a background on that group instead. In that group you then put all the content you want on that “row/box”.
There´s many good reasons to do it like this instead of just setting elements, like text, directly in the reaping group´s cell. This way you can control what you want to show in the list much more.
One being the color of the background of the “lines”.
So let´s say you set the standard background of the group (within the repeating group) to white.
Then you set a condition on the group as on the screenshot below.
This way every second row will be white and the others grey (in this case). Since evert second cell this statement will be true and in the others not.
I think and hope this answers both your questions?!
Good luck!