Button bg was no good in Chrome

_sass/support/mixins/_buttons.scss

@@ -2,12 +2,14 @@
 
 @mixin btn-color($fg, $bg) {
   color: $fg;
+  background-color: darken($bg, 2%);
   background-image: linear-gradient(lighten($bg, 5%), darken($bg, 2%));
   box-shadow: 0 1px 3px rgba(0, 0, 0, 0.25), 0 4px 10px rgba(0, 0, 0, 0.12);
 
   &:hover,
   &.zeroclipboard-is-hover {
     color: $fg;
+     background-color: darken($bg, 4%);
     background-image: linear-gradient((lighten($bg, 2%), darken($bg, 4%)));
   }