change colour from mailbox in Mac Mail Is it possible to change the color of the mailboxes in Mac Mail? 

Here an example



Sometimes I manage to create Silver colored mailboxes by accident so I am wondering if it is possible to label them with other colors than silver and blue.
No.  A silver coloured mailbox indicates that you deleted a subfolder within that mailbox.  You need to remove the parent after removing all of the subfolders.  Then the parent will disappear as expected.