What exactly do you want to change? Post a picture if necessary. It is possible to change the colour of the folder name in the Folder Pane that has new mail. It's also possible to change the number of unread shown in the circle next to a folder.

Hello

Take a look Change "Unread email" color...again! https://connect.mozilla.org/t5/discussions/change-quot-unread-email-quot-color-again/td-p/48163

Sorry for the delay in returning here; I've been under the weather. I guess my original question was really ambiguous. I'm very sorry. I'm afraid my previous wording may lead to answers I don't need. Let me try again. The latest Thunderbird update makes the modifications that I currently have in my chrome file non-functional & I would like to fix that but don't know how. The number of unread emails in a given folder is now shown off to the side of each folder name ( main folders as well as the many local folders ) as a number over a gray background. If there are new emails the background is blue. I would like to change the "new emails" color to the shade of red I was previously using. It was called "tomato" if I remember. I remember that the code for this color change had to replace another snippet of code and maybe had to be in a certain position in the file (?) with a certain header in the file (?)...maybe. Does the code that Agent virtuel posted the link to do that? I haven't yet had the time to try to decipher all of that. Thanks.

I think your wish can be accomplished, but you need to post a screenshot of the exact item to be changed.

Here is some code that styles the unread counter:

https://support.mozilla.org/en-US/questions/1426787#answer-1611024