.mce-ico.mce-i-gfycatGifButton {
  font: normal 20px/1 'dashicons';
  padding: 0;
  vertical-align: top;
  speak: none;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  margin-left: -2px;
  padding-right: 2px;
  background-image: url('gfycat_logo_grey.svg');
}

.mce-ico.mce-i-gfycatGifButton:hover {
  background-image: url('gfycat_logo_blue.svg');
}