outline thickness and / or color / shading of just the active cell in Excel

Hello Stan,

Thank you for posting in Microsoft Community. Based on the description you posted, you wish to make the active cell more apparent by customizing it, however, this is not an option in Excel for now. Although, some users add-ins, which we don't recommend.

Excel uses the default green border to highlight the active cell or to make it noticeable, however, since the option to customize this outline is not available, you can try the steps below as a workaround which may work for you.

   1. Click on the "File" tab in the ribbon and select "Options".

   2. In the "Excel Options" dialog box, select "Advanced" from the left-hand pane.

   3. Scroll down to the "Display options for this worksheet" section and uncheck the box next to " Show Gridlines" then click OK

   4. If this setting does not work for you, you can try to change the grid color to gray or any color you wish to use to make the green outline of the     active cell more apparent. 

You can try to change the Office them to dark gray by going to File > Account > Office Background and choose dark gray. However, there's only 3 options by default and see if the dark gray will work for you, if not you can keep the office background that you're using.

For now, we can only provide workarounds, we suggest to send your feedback or suggestions to help Microsoft improve the application. Please check this link as your reference How do I give feedback on Microsoft 365? - Microsoft Support.

I hope this helps.

Regards,

Nhiel T.

Microsoft Moderator