First introduced in Une Boutique 2.1.6 you can now have separator styles between rows. As usual the options can be found in the row editor pop up, under Extra Options tab. Right now there are only two styles available, but there will be more soon.
All you have to do is to Select a separator style and then give it a color. Keep in mind that the separator appears always at the bottom of the row, so the color given to it should match the background color of the next row. If the next row has no background color set to it, it mean that it is using the default background color of the page which is #FAFAFA so the separator should have it’s default color, just leave the color empty and it will have #FAFAFA as it’s color.