To change Gridline color in Excel, use Excel Options, apply a custom-colored border to the cells, or apply a custom line color. Full details here.

I'm creating a utility in Excel that takes mesh bad leveling raw data (49 values, 7x7 grid, with the center value being what all other values are being compared to). Some values are positive, some ...

In case of an error, a triangle appears in the corner of the cell. You can change the Color of an Error Indicator from green to any other in Excel.