Hi,
I have a calc spreadsheet in which the first line is reiterated on the top of every new page. When I now use any background color for one complete row, the lower grid line of that first line (or upper grid line of the cell below) is always missing, both in the preview and in the printed document. All the other grid lines in the whole document and in the colored row are being shown just fine.
When you copy & paste a cell from one place to another, it can copy the formatting also, depending on your chosen paste settings. What probably happened at some point is that you pasted into the cell that has no top border by copying from a cell that has no borders, and the pasted formatting removed the border from all sides of that one cell. You should be able to add the border again. If you don’t want this to happen, you will have to be careful to paste cell values & formulas only, and not formatting. It can be a pain to remember sometimes.
While adding the border back in, you can hold down SHIFT when clicking the bottom or top border toolbar icon to ensure it overwrites the formatting. This behavior is different than what I’m used to in Excel, so I just learned something new by experimenting! 
In Excel, I believe borders are shared between adjacent cells, so changing the top of one cell effects the bottom of the cell above. Looks different (and a tad confusing) in Calc.
Menu/Tools/Options/LibreOffice calc/View - Visual aids - Grid lines - Show on colored cells
awesome, worked perfectly
Please, if the answer solves the question click 
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