You can change the default color of chart, graph, treemap, etc. in Word, Excel, and PowerPoint with the helpof these simple steps.

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.