Templates styles were changed in UNA 12, as the result it maybe some issues if you have custom styles, to fix them I would suggest you to create new style mix which is clones from one of the default styles and then change it as you need.
That didn't seem to help. Even the default or system icon background has changed and I have no way to change just the background color. I can change the icon and/or link colors but not the icons background color.
