Chartjs-Pie Chart using chart.js not showing up but bar charts are?

Try Using :

new Chart(document.getElementById("pieChart"), {
type: 'pie',
  data: {
  labels: ["Green", "Blue", "Gray", "Purple", "Yellow", "Red", "Black"],
  datasets: [{
     backgroundColor: ["your color list"],
         data: [12, 19, 3, 17, 28, 24, 7]
         }]
        }
      });