How to customize the background/border colors of a grouped table view?

I would like to customize both the background and the border color of a grouped-style UITableView.

I was able to customize the background color by using the following:

tableView.contentView.backgroundColor = [UIColor greenColor];

But the border color is still something I don't know how to change.

How do I customize these two aspects of the grouped-style table view?

Source: Tips4all