.block-pfpca-footer-friends-and-sponsors img{
  max-height:100px;
  -webkit-filter: grayscale(100%);
  filter: grayscale(100%);
  -webkit-transition: -webkit-filter .4s;
  transition: filter .4s, -webkit-filter .4s;
}

.block-pfpca-footer-friends-and-sponsors img:hover,
.block-pfpca-footer-friends-and-sponsors img:focus{
  -webkit-filter: grayscale(0%);
  filter: grayscale(0%);
}