Set color in addition to fill for the icon class

Structure icons have fill set to currentColor hardcored in their markup.
This mean setting fill to a color in CSS does nothing, but setting color
now does.

ui/app/styles/core/icon.scss

@@ -42,6 +42,7 @@ $icon-dimensions-large: 2rem;
 
     &.is-#{$name} {
       fill: $color;
+      color: $color;
     }
   }
 }