found the window styling settings:

While in game, go to Config/windows and go down to the bottom line of numbers. These are the different window styles.

Sounds like you may be on style 1. If you set it to 5, it makes the background color for that message bar a transparent gray and it leaves you with just the thin white borders that I have. that background applies to all the backgrounds too, so you can see thorugh your chat line and other menus better as well.