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.

The default active cell format in Microsoft Excel isn't all that easy to see, but you can use this easy-to-implement code solution to change that.

In Microsoft Excel, if a cell contains a formula that results in an error, a triangle appears in the top-left corner of the cell. The triangle is an error indicator.