subtitle.border.color String (default: "black")

The color of the border. Accepts a valid CSS color string, including hex and rgb.

Example - set the chart subtitle border color

<div id="chart"></div>
<script>
$("#chart").kendoChart({
  title: {
    text: "Title"
  },
  subtitle: {
    text: "Subtitle",
    border: {
      color: "green",
      width: 2
    }
  },
  series: [
    { data: [1, 2, 3] }
  ]
});
</script>