There were serious issues with the old and beloved folder icons. The old icons were actual image files and unfortunately not scalable which for years posed real problems for some people. The update was due to improving the accessibility so that it was inclusive for all.

The new icons are created differently because they are SVG (sacalable vector graphics) which means they are scalable. So there you go, now you know the reason was to be inclusive for those with particular needs.

The icons can be coloured as you choose. This can be done manually:

• Right click on folder and choose 'Properties'
• On the 'General Information' tab there is a 'Icon Colour' option.
• Click on the coloured rectangular box and choose whatever colour you prefer.
• click on OK.
• Click on OK to exit Properties.

There is another way of setting them, but it involves creating a 'userChrome.css' file. The beauty of that means all are auto coloured to your setting eg: set all Inboxes as green and new folders get the auto colour instead of needing a manual change each time. I would supply all the code, you would just have chose the colours and follow instructions. If you are interested I will post that info in a separate comment.

Hi Toad-Hall,

Yes, I've just manually added all the files for one folder and it took quite some time so I would appreciate the css file and the appropriate location for it. (Especially if that means I can make them keep their new colour even when they're highlighted, because currently they default to black again)

Cheers,

Alex

This is not so difficult as it only requires you being able to follow instructions, create folders and files; copy and paste text. The only bit you need to sort out is the actual colour which I've shown as bold.

First make sure this is set as follows:

• Menu app icon > Options
• Select 'General'
• Scroll to the bottom and click on 'Config Editor' button
• Accept Dragons warning
• In search type: legacy
• Look for this line: toolkit.legacyUserProfileCustomizations.stylesheet

If it is set to 'True' then all is OK

If it is set to 'False'

• Double click on that line to toggle the 'False' to 'True'
• Restart Thunderbird if you needed to alter the setting.

Now to create the userChrome.css file: In Thunderbird:

• Help > Troubleshooting Information
• click on 'Open folder' button

a new window opens showing the contents of your Profile folder.

• Close Thunderbird now - this is important.
• Create new folder and call it chrome note the spelling - use a lower case 'c' It should be in the same place as the 'Mail' folder. See image below as guide.

• open Notepad
• Copy everything - all the text between lines below and paste it into the Notepad document.

note: In the code below, all the colours are represented as html hex code which is the # key followed by 6 numbers/letters eg: #ff0000. You can see just above each code section I've written some text to say what colour I used and in the image below, it shows how this looks using dark theme. Basically red for account; green for good default folders; orange for junk and trash; special search folder turqiouse and all others set as yellow. But you can choose whatever colour you want. The link below will help you choose colours and show hex codes. https://www.w3schools.com/colors/colors_picker.asp

/*
* Do not remove the @namespace line -- it's required for correct functioning - it only needs to be entered once at the top of the userChrome.css file
 */

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); 


/* remove this section of code -  if you do not want to preset all folders you created with same colour */
/* all other folders - not special folders - yellow*/
treechildren::-moz-tree-image(folderNameCol){
  fill: #ffff00 !important;
}


/* this changes only mail account folders to red */
treechildren::-moz-tree-image(folderNameCol, isServer-true) {
  fill: #ff0000 !important;
}

/* ..... Inbox - colour green ..... */
.tabmail-tab[type="folder"][SpecialFolder="Inbox"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Inbox) {
  fill: #33cc33 !important;
 
}

/* ..... Sent - green..... */
.tabmail-tab[type="folder"][SpecialFolder="Sent"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Sent) {
  fill: #33cc33 !important;
}


/* ..... Outbox - green..... */
.tabmail-tab[type="folder"][SpecialFolder="Outbox"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Outbox) {
  fill: #33cc33 !important;
}

/* ..... Drafts - green..... */
.tabmail-tab[type="folder"][SpecialFolder="Drafts"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Drafts) {
  fill: #33cc33 !important;
}


/* ..... Archives - green ..... */
.tabmail-tab[type="folder"][SpecialFolder="Archive"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Archive) {
  fill: #33cc33 !important;
}

/* ..... Templates - green..... */
.tabmail-tab[type="folder"][SpecialFolder="Templates"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Templates) {
  fill: #33cc33 !important;
}

/* ..... Junk - orange ..... */
.tabmail-tab[type="folder"][SpecialFolder="Junk"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Junk) {
  fill: #FF9900 !important;
}

/* ..... Trash  orange ..... */
.tabmail-tab[type="folder"][SpecialFolder="Trash"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Trash) {
  fill: #FF9900 !important;
}

/* ..... Saved Search Folder  turquoise..... */
.tabmail-tab[type="folder"][SpecialFolder="Virtual"],
treechildren::-moz-tree-image(folderNameCol, specialFolder-Virtual) {
  fill: #33cccc !important;
}

Please note: recently, emails containing code were missing one vital part - !important; was removed from code - the info is all correct in the forum question, but somehow got changed when the comment was posted to recipient in email - so please double check.

• Save the document as filename userChrome.css in the 'chrome' folder. Note the spelling all lower case except for the 'C'. See image below as guide.

• Start Thunderbird.

This means that if you were to add another mail account or folder then the colours will get set automatically. It does mean you cannot change them manually.