.ngg-gallery-thumbnail {
    background-color: #fff;
    border: 1px solid #45a8a6;
    display: block;
    margin: 4px 0 4px 4px;
    position: relative;
}

.ngg-gallery-thumbnail:hover {
    border: 1px solid #45a8a6;
    margin: 4px 0 4px 4px;
    background-color: #45a8a6;
}