.clients_slider {
    margin-top: 30px;
}

.clients_slider img {
    display: block;
    margin: 0 auto;
    width: 70%;
    -webkit-filter: grayscale(100%);
    filter: grayscale(100%);
    opacity: .7;
    -webkit-transition: all .3s ease;
    -moz-transition: all .3s ease;
    transition: all .3s ease;
}

.clients_slider img:hover {
    -webkit-filter: grayscale(0%);
    filter: grayscale(0%);
    opacity: 1;
}