
@Tuneap1st ,
Welcome to Q&A forum!
Based on my research and testing, you may not be able to achieve this through GPO.
I would suggest you put the custom colors into a theme and export it, then distribute the theme file( .thmx) into the Document Themes path of other users.
- Open a blank Word document and customize your color palette.
- Click the Save Current Theme to save the theme with custom colors to path C:\Users\<User Name>\AppData\Roaming\Microsoft\Templates\Document Themes.
If you perform this behavior in Word, the Excel and PowerPoint on the same machine will automatically load this theme.
For more information, you could refer to Change a theme and make it the default in Word or Excel.
Hope the information could be helpful to you.
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