Edit in JSFiddle

var Settings = {
  container: document.getElementById("guitar-tuner"),
  backgroundColor: "white", // or hex colors "#ffffff"
  notOkayColor: "orange",
  okayColor: "green",
  fontColor: "black"
};

function initializeTuner() {
  // Create a single or multiple instance of tuners at time
  var tuners = [
    new OnlineTuner.Controller.GuitareTuner(
      new OnlineTuner.Widget.CircleWidget(
        Settings.container, 
        Settings.backgroundColor, 
        Settings.notOkayColor, 
        Settings.okayColor, 
        Settings.fontColor
      )
    )
  ];

  // Initialize the tuner with the callbacks
  new OnlineTuner.Analyser(tuners).install(function() {
    console.log("Succesfully initialized");

  }, function(errorMessage) {
    console.error("Oops, this shouldn't happen", errorMessage);
  });
}
  
    // Render the guitar tuner on the canvas by running the function
initializeTuner();

<canvas id="guitar-tuner" height="300"></canvas>