<!DOCTYPE html> <html> <body> <canvas id ="output" width="100" height="100"></canvas> <script> var canvas = document.getElementById('output'); var ctx = canvas.getContext('2d'); var colors = ['red', 'green', 'blue']; for (var i = 2; i >= 0; i--) { ctx.fillStyle = colors[i]; ctx.fillRect(i * 20, i * 20, 40, 40); } </script> </body> </html>