Cambio de Colores

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

<script>
    var pantalla = document.querySelector("canvas");
    var pincel = pantalla.getContext("2d");

    pincel.fillStyle = "lightgrey";
    pincel.fillRect(0, 0, 600, 400);

    function cambiarColor() {

        var colores = ["blue", "red", "green", "yellow", "orange"];

        if (colorActual == colores[0]) {
            pincel.fillStyle = colores[1];
            colorActual = colores[1];
        } else if (colorActual == colores[1]) {
            pincel.fillStyle = colores[2]
            colorActual = colores[2];
        } else if (colorActual == colores[2]) {
            pincel.fillStyle = colores[3]
            colorActual = colores[3];
        }else if (colorActual == colores[3]) {
            pincel.fillStyle = colores[4]
            colorActual = colores[4];
        }
        else {
            pincel.fillStyle = colores[0];
            colorActual = colores[0];
        }
    }

    function dibujarCirculo(evento) {
        var x = evento.pageX - pantalla.offsetLeft;
        var y = evento.pageY - pantalla.offsetTop;
        pincel.beginPath();
        pincel.arc(x, y, 10, 0, 2 * 3.14);
        pincel.fill();
    }

    var colorActual = "blue";
    pincel.fillStyle = "blue";
    pantalla.onclick = dibujarCirculo;
    pantalla.oncontextmenu = cambiarColor;

</script>