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.

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.

How to Change the Color Coding on a Microsoft Excel Graph Legend. Color can make it easier for people to identify important information, such as legends on an Excel graph. Professional designers ...