Bandeira

<canvas width="600" height="400" ></canvas>

<script>

    var tela = document.querySelector('canvas');
    var pincel = tela.getContext('2d');

    //verde
    pincel.fillStyle = 'green';
    pincel.fillRect(0, 0, 600, 400);

    //amarelo
    pincel.fillStyle = 'yellow';
    pincel.beginPath ();
    pincel.moveTo(300, 50);
    pincel.lineTo(50, 200);
    pincel.lineTo(550, 200);
    pincel.fill();

    //amarelo2
    pincel.fillStyle = 'yellow';
    pincel.beginPath ();
    pincel.moveTo(300, 350);
    pincel.lineTo(50, 200);
    pincel.lineTo(550, 200);
    pincel.fill();

    //azul
    pincel.fillStyle = 'darkblue';
    pincel.beginPath();
    pincel.arc(300, 200, 100, 0, 2*3.14);
    pincel.fill();


</script>