* Adding button.color code.

gtk-3.20/scss/widgets/_choosers.scss

@@ -139,7 +139,22 @@
        }
     }
 
-    button.color { padding: $spacing; }
+    button.color {
+        padding: $spacing;
+
+        colorswatch:only-child {
+            &, overlay { border-radius: 0; }
+
+            @if $variant == 'light' { box-shadow: 0 1px _text_shadow_color(); }
+        }
+
+        @if $variant == 'light' {
+            &:disabled,
+            &:backdrop,
+            &:active,
+            &:checked { colorswatch:only-child { box-shadow: none; } }
+        }
+    }
 
     colorchooser .popover.osd { border-radius: $roundness; }
 }