Solucion ejercicio - Cambiando de color

<meta charset="UTF-8">
<canvas class="myCanvas" width="600" height="400">

</canvas>

<script>

 var canvas = document.querySelector(".myCanvas");
 var pincel = canvas.getContext("2d")
 var colores = ['blue','red','green']
 var incremetar = 0
 var color = colores[0]



 pincel.fillStyle='gray'
 pincel.fillRect(0,0,600,400)


 function exibirAlerta(evento){
    var x = evento.pageX - canvas.offsetLeft
    var y = evento.pageY - canvas.offsetTop

    console.log(evento)
    alert(x+","+y)
 }


 function dibujarCirculo(evento){
    var x = evento.pageX - canvas.offsetLeft
    var y = evento.pageY - canvas.offsetTop

    pincel.fillStyle=color
    pincel.beginPath()
    pincel.arc(x, y, 10,0,2*Math.PI)
    pincel.fill()


 }

 canvas.onclick = dibujarCirculo

 function alterarColor() {
    alert("Funcionó")
    if(incremetar != (colores.length -1)){
        color = colores[incremetar+=1]
        console.log(color)
    }else{
        color = colores[0]
        incremetar = 0 
        console.log("reset color "+color)
    }

 }

canvas.oncontextmenu = alterarColor


</script>