.grayscale {
   -webkit-filter: grayscale(100%);
   -moz-filter: grayscale(100%);
   filter: grayscale(100%);
   transition: all 0.5s ease;
}
.grayscale:hover{
    -webkit-filter: grayscale(0%);
   -moz-filter: grayscale(0%);
   filter: grayscale(0%);
}