A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Hi Guy,
I think you may be confusing two different concepts: gridlines vs cell borders. These look like the same thing, but they are not.
You format gridlines using Menu Bar > Excel > Preferences > View where you can set the color of gridlines.
Cell borders are formatted independently of the gridlines. Select a cell or range and press Command-1 to format the borders.
I suggest you experiment with these settings until you get the result you desire.