GoogleMapをモノクロ・マウスオンで元の色付き地図に

.gmap iframe,
.gmap object,
.gmap embed {
  -webkit-filter: grayscale(100%);
  -moz-filter: grayscale(100%);
  -ms-filter: grayscale(100%);
  -o-filter: grayscale(100%);
  filter: grayscale(100%);
  -webkit-transition: all 0.7s ease;
  -moz-transition: all 0.7s ease;
  -o-transition: all 0.7s ease;
  transition: all  0.7s ease;
}

.gmap iframe:hover,
.gmap object:hover,
.gmap embed:hover {
  -webkit-filter: grayscale(0%);
  -moz-filter: grayscale(0%);
  -ms-filter: grayscale(0%);
  -o-filter: grayscale(0%);
  filter: grayscale(0%);
}