Legend.inactiveItems

<div id="stock-chart"></div>
<script>
$("#stock-chart").kendoStockChart({
    legend: {
        inactiveItems: {
            labels: {
                color: "gray"
            }
        }
    },
    series: [{
        name: "Series 1",
        type: "line",
        data: [
            { date: new Date(2023, 0, 1), value: 10 },
            { date: new Date(2023, 0, 2), value: 20 },
            { date: new Date(2023, 0, 3), value: 15 }
        ],
        visibleInLegend: false
    }]
});
</script>

<div id="stock-chart"></div>
<script>
$("#stock-chart").kendoStockChart({
    legend: {
        inactiveItems: {
            labels: {
                color: "lightgray",
                font: "12px Arial"
            }
        }
    },
    series: [{
        type: "line",
        data: [
            { date: new Date(2023, 0, 1), value: 10 },
            { date: new Date(2023, 0, 2), value: 20 },
            { date: new Date(2023, 0, 3), value: 15 }
        ]
    }]
});
</script>

<div id="stock-chart"></div>
<script>
$("#stock-chart").kendoStockChart({
    legend: {
        inactiveItems: {
            markers: {
                color: "lightgray"
            }
        }
    },
    series: [{
        type: "line",
        data: [
            { date: new Date(2023, 0, 1), value: 10 },
            { date: new Date(2023, 0, 2), value: 20 },
            { date: new Date(2023, 0, 3), value: 15 }
        ],
    }]
});
</script>