By default , the cell border color in Microsoft Excel is grey. You can change the border color of the cell in Excel and this blog post will demonstrate how to change the border color of multiple cells.
How to change the border color of multiple cells in Excel?
1. In the Home tab , click the array besides the Border button which is found under the Font group.
2. In the drop-down list , mouse over the Line color item and select fit color
3. The cursor becomes a pencil. Hold down the Ctrl key and then drag the pencil through selection that you want to change its cell border color.
This would change the border color of the selected cells.