.tracking-activated,
.tracking-activated:hover {
  background: #0074d9 url(img/GPS_on.png);
  background-size: cover;
  background-position: center center;
  background-repeat: no-repeat;
}

.tracking-deactivated,
.tracking-deactivated:hover {
  background-image: url(img/GPS_off.png);
  background-size: cover;
  background-position: center center;
  background-repeat: no-repeat;
}