Is it possible to place a gap between rows and maybe even give it a color?
If it's really important to you to place a color between the rows, then you could do it using a CreationFilter or a DrawFilter. But it's not trivial to implement.
Grid.DisplayLayout.Override.RowSpacingAfter (RowSpacingBefore also exists). As far as coloring... there are no other UI Elements there so it will pick up the color from the background of the grid by default.