fonts/j6.svg

<svg width="32" height="32" xmlns="http://www.w3.org/2000/svg">
  <rect class="background" width="100%" height="100%" />
  <style>
    .background {
      fill: white;
    }

    text {
      font-size: 1.6em;
      text-anchor: middle;
      fill: black;
    }

    @media (prefers-color-scheme: dark) {
      .background {
        fill: black;
      }

      text {
        fill: white;
      }
    }
  </style>
  <text x="50%" y="50%" dominant-baseline="central">6</text>
</svg>