There were loads of comments from people who disliked the bland grey outline of icons in folder pane. So, it is understandable why they offered an improvement from the grey. You say you do not like the new set of default folders, but you do not say what you do want. what do you mean by: "Please tell me, there's a way to give back Thunderbird a professional appearance." Please understand, all icons as outline eg: grey is not necessarilly considered 'professional'. I've still got all the original folders used way back in 68* and I'm using them in version 102* So I've just gone into Troubleshoot mode to see the latest icons. Looks like they are using what could be described as a more traditional colour format - eg: folders are yellow As in previous grey icon design you always had the option of choosing a colour for the folders. This is still the case. Right click on folder and select 'Properties' Use the 'Icon colour' option to change the colour. As you are using a MAC, please remember - after choosing the colour you need to close the colour picker window before clicking on ok.