[Chartjs]-Chart JS Line Graph multitooltipkey background color issue

It’s a 2 part answer if I follow correctly:

1.- Specify colors on your data set:

var data = {
  labels: ["January", "February", "March", "April", "May"],
  datasets: [{
    label: "Series A",
    data: [10, 30, 20, 40, 10],
    borderColor: "rgba(0,0,255,0.8)",
    backgroundColor:"rgba(0,0,255,0.5)"
  }, {
    label: "Series B",
    data: [25, 40, 10, 40, 30],
    borderColor: "rgba(255,0,0,0.8)",
    backgroundColor:"rgba(255,0,0,0.5)"
  }]
};

And enable the tooltips on the options Object (Notice the mode Label):

var options = {
  tooltips: {
   enabled: true,
   mode: 'label'
 },          
  legend: {
    display: true,
  }  
};

Result:

Codepen:

Codepen – Chart.js Multiline Tooltip labels