It is 50% transparent in the chat area and 25% transparent in the quickslot area, to make the two regions distinct, while retaining the default tan outline.
The file needs to be in the ovr folder for nwn enhanced or the override folder for regular nwn.
For example c:\Path To Steam\steamapps\common\Neverwinter Nights\ovr).
https://drive.google.com/file/d/1cuyD6K ... sp=sharing