Hello, gentlemen! I have a small problem. I don't know how to change the color of the Menu bar to gray? Please help! Thanks! (I used Thunderbird version 138.0.1)

That color doesn't look like a default option. Have you tried changing themes?

I tried changing themes (I have a light, dark, and another theme that I installed), but the Menu bar still remains black. I don't know where the problem could be.

Are you using any CSS or maybe an addon that changes color? Color changes are usually done with custom changes.

I have the Phoenity Icons addon installed (to change the look of the icons), Auto profile picture and Auto Avatars. I didn't use any css file. Do you suggest I restore the entire Thunderbird and reinstall it?

Reinstalling rarely fixes anything, and sometimes causes problems. I suggest clicking help>troubleshoot mode and restart with addons disabled and see how that works. The fact that your menu bar is above the unified toolbar caused me to infer that you are using the usercontrol.css file with customizations.

Mr. david, Thank you so much! It worked! :-)

Cheers, Igor

You are most welcome. :)