<canvas widht="600" height="400"></canvas>
<script>
var tela = document.querySelector("canvas");
var pincel = tela.getContext("2d");
pincel.fillStyle = "lightgrey";
pincel.fillRect(0, 0, 600, 400);
pincel.fillStyle = "green";
pincel.fillRect(0, 0, 100, 400);
pincel.fillStyle = "red";
pincel.fillRect(200, 0, 100, 400);
