When setting background for labels explicitly the labels in admin will

overlap the `::before` pseudo-element.

I suggest to remove explicit setting for `label` element or replace
`@color-white` to `transparent`.

In some cases developers try to hide elements by setting white
background and higher z-index for the element with white background.
But the proper way of hiding elements is to override templates config or
remove elements by JavaScript.

Author: TomashKhamlai

app/design/adminhtml/Magento/backend/web/css/source/forms/_fields.less

@@ -545,7 +545,6 @@
             & > .admin__field-label {
                 #mix-grid .column(@field-label-grid__column, @field-grid__columns);
                 cursor: pointer;
-                background: @color-white;
                 left: 0;
                 position: absolute;
                 top: 0;