body {width: 600px; height: 600px;margin: 100px auto;text-align: center}
div {margin: 0 auto}

single-item col-6 col-lg-4 {
      filter: gray; 
      -webkit-filter: grayscale(1); 
      -webkit-transition: all .8s ease-in-out;  
    }

    single-item col-6 col-lg-4:hover {
    filter: none;
      -webkit-filter: grayscale(0);
      -webkit-transform: scale(1.01);
    }