The Tags tab of Preferences/Display should look like the attached picture, at least in Windows, where the name of the tag matches the tag color. Does it look different if you run in safe mode (hold Option when you launch TB)?

I disabled the extention "Theme Font & Size Changer for Thunderbird." All is well. Thank you, Major

I now have an issue of "small" point size in the email and file folder listings. I tried Zoom, but no go.

It's possible to adjust the fonts for the Threads Pane and Folder Pane without using the TF&SC add-on. Create a folder named chrome in the profile folder, and inside chrome create a userChrome.css file with a text editor, The content of the css file is given here.

I am using an Apple MacBook Air and know not how to place such a file in profile.

Select Help/Troubleshooting Information, click Show in Finder to open the profile folder in Finder, close TB, then follow the instructions above to create the chrome subfolder and the userChrome.css file. This tutorial is for Firefox, but the general approach is the same for TB.

I created the userChrome.css file, placed it in the Profile folder, restarted in "safe" mode, but no change.

Start in normal mode, as safe mode ignores userChrome.css files. Also, the css file must be in the chrome subfolder of the profile folder, not the profile folder.

I created a chrome folder (there was no chrome older) in the profile folder. I then placed the userChrome.css file into the chrome folder. I restarted TB in normal mode, but the point size is still small.

Correction. I forgot to remove the '.txt' suffix from the file. It now appears normal. The point size is slightly large than before but I can read it now with relative ease.

Thank you, Major

You can change the parameters in the css file until it looks satisfactory, e.g. increase the 12pt font size to 14pt or 16pt. Adjust the cell height too if necessary.

That looks much better. Thank you, Major