Suppress IE/Edge additional white/blue colors for focused <select>

scss/_custom-forms.scss

@@ -159,6 +159,16 @@
     border-color: $custom-select-focus-border-color;
     outline: none;
     @include box-shadow($custom-select-focus-box-shadow);
+
+    &::-ms-value {
+      // For visual consistency with other platforms/browsers,
+      // supress the default white text on blue background highlight given to
+      // the selected option text when the (still closed) <select> receives focus
+      // in IE and (under certain conditions) Edge.
+      // See https://github.com/twbs/bootstrap/issues/19398.
+      color: $input-color;
+      background-color: $input-bg;
+    }
   }
 
   // Hides the default caret in IE11