}
    return elem;
  }

  function makeColor(index) {
    // Rotate hue around a circle. Multiple by phi to spread things
    // out better. Use 50% saturation to make subdued colors, and
    // 80% lightness to have good contrast with black foreground text.
    const PHI = 1.618033988;
    const hue = (index+1) * PHI * 2 * Math.PI; // +1 to avoid 0
    const hsl = `hsl(${hue}rad 50% 80%)`;
    return hsl;
  }
}