Firefox grayscale

I have an image which i have set to grey, but which I want to be in full colour on hover. It works fine in Chrome but the grayscale remains in firefox. Any suggestions?

.greyimage {
  -webkit-filter: grayscale(100%);
  -moz-filter: grayscale(100%);
  -o-filter: grayscale(100%);
  -ms-filter: grayscale(100%);
  filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0\'/></filter></svg>#grayscale"); /* Firefox 10+, Firefox on Android */
  opacity: .5;
}

.greyimage:hover {
  -webkit-filter: grayscale(0%);
  -moz-filter: grayscale(0%);
  -o-filter: grayscale(0%);
  -ms-filter: grayscale(0%);
  opacity: 1;
}

Solution

filter option is the one that makes Firefox show your image grayscaled. You should reset it on hover.

.greyimage {
  filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0\'/></filter></svg>#grayscale"); /* Firefox 10+, Firefox on Android */
  filter: gray; /* IE6-9 */
  -webkit-filter: grayscale(100%); /* Chrome 19+, Safari 6+, Safari 6+ iOS */   
}

.greyimage:hover {
  filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'1 0 0 0 0, 0 1 0 0 0, 0 0 1 0 0, 0 0 0 1 0\'/></filter></svg>#grayscale");
  filter: none;
  -webkit-filter: grayscale(0%);
}