superset/assets/visualizations/chord.css

.chord svg #circle circle {
    fill: none;
    pointer-events: all;
}

.chord svg .group path {
    fill-opacity: .6;
}

.chord svg path.chord {
    stroke: #000;
    stroke-width: .25px;
}

.chord svg #circle:hover path.fade {
    opacity: 0.2;
}