figure.wp-block-table table.has-fixed-layout {
    border-bottom-color: rgb(128, 128, 128);
    border-collapse: collapse;
    border-left-color: rgb(128, 128, 128);
    border-right-color: rgb(128, 128, 128);
    border-top-color: rgb(128, 128, 128);
}

figure.wp-block-table table.has-fixed-layout thead {
    border-bottom-color: rgb(0, 0, 0);
    border-bottom-style: solid;
    border-bottom-width: 3px;
    border-collapse: collapse;
    border-left-color: rgb(128, 128, 128);
    border-right-color: rgb(128, 128, 128);
    border-top-color: rgb(128, 128, 128);
}

figure.wp-block-table table.has-fixed-layout tbody {
    border-bottom-color: rgb(128, 128, 128);
    border-collapse: collapse;
    border-left-color: rgb(128, 128, 128);
    border-right-color: rgb(128, 128, 128);
    border-top-color: rgb(128, 128, 128);
}

figure.wp-block-table table.has-fixed-layout td {
    border: 1px solid;
    padding: .5em;
}