Chartjs-Custom Tooltips On Line Chart Using Chart.js

Custom Labels for Each Dataset

You can do this by using a custom label object.

Preview

Script

function TeamPlayerLabel(label, team1Label, team2Label) {
    this.label = label;
    this["Team 1"] = team1Label;
    this["Team 2"] = team2Label;
}
TeamPlayerLabel.prototype.toString = function () {
    return this.label;
}

var data = {
    labels: [
        new TeamPlayerLabel("Player 1", "John Red", "John Green"),
        new TeamPlayerLabel("Player 2", "Mark Red", "Mark Green"),
        new TeamPlayerLabel("Player 3", "Jane Red", "Jane Green"),
        new TeamPlayerLabel("Player 4", "Jill Red", "Jill Green"),
    ],
    datasets: [
        {
            label: "Team 1",
            ...
        },
        {
            label: "Team 2",
            ...
        }
    ]
};

and then

new Chart(ctx).Line(data, {
    multiTooltipTemplate: function (self) {
        return self.label[self.datasetLabel] + ': ' + self.value;
    }
});

Fiddle – https://jsfiddle.net/htq3kgay/