ConnectionDefaults.hover

<div id="diagram"></div>
<script>
  $("#diagram").kendoDiagram({
    shapes:[
      {
        id:"1",
        content:{
          text: "State 1"
        },
        x: 20,
        y: 20
      },
      {
        id:"2",
        content: {
          text: "State 2"
        },
        x: 200,
        y: 20
      }
    ],
    connections:[
      {
        from: "1",
        to: "2"
      }
    ],
    connectionDefaults: {
      hover: {
        stroke: {color: "red", width: 2}
      },
      stroke: {
        color: "#979797",
        width: 4
      },
      type: "polyline",
      startCap: "FilledCircle",
      endCap: "ArrowEnd"
    }
  });
</script>

<div id="diagram"></div>
<script>
$("#diagram").kendoDiagram({
    connectionDefaults: {
        hover: {
            stroke: {
                color: "#FF6600",
                width: 3
            }
        }
    },
    shapes: [
        { id: "1", x: 100, y: 100, content: { text: "Shape 1" } },
        { id: "2", x: 300, y: 100, content: { text: "Shape 2" } }
    ],
    connections: [
        { from: "1", to: "2" }
    ]
});
</script>