Changing the color of worksheet gridlines in Excel is a quick and easy way to add some visual interest to your data. Here's how to do it:

1. Open your Excel workbook. Go to the worksheet that you want to change the gridline color for. Right-click on any cell in the worksheet and select Format Cells from the popup menu.
2. Select the Border tab. In the Line Color dropdown, select the color that you want your gridlines to be. If you want to make your gridlines thicker or thinner, you can use the Weight dropdown.
3. Click OK.