It is a Voronoi diagram (https://mathworld.wolfram.com/VoronoiDiagram.html) where each point is a web color as it would be positioned on a full hue-saturation color wheel.

It's cheating a bit and using `saturation + brightness / 5` as radius. This separates colors with the same saturation and hue, in particular grays.

    // Based on https://stackoverflow.com/a/54522007/91238 .
    // I've tweaked it to spread out some of the colors (especially they greys)
    // that don't fit well into a true H/S wheel.
    let colorRadius = (s + v/5)*0.75 * radius;
    let colorAngle = h/360 * 2 * Math.PI;