Esta es mi version del codigo.
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Change Color</title>
</head>
<body>
<h1>Change Color</h1>
<canvas width="600" height="400" id="lienzo"></canvas>
<script type="text/javascript" src="script.js"></script>
</body>
</html>JavaScript
var lienzo = document.querySelector("canvas");
var pincel = lienzo.getContext("2d");
pincel.fillStyle = "grey";
pincel.fillRect(0,0,600,400);
let colors = ["blue","red","green"];
let indiceColor = 0
function dibujarCirculo(evento){
var x = evento.pageX - lienzo.offsetLeft;
var y = evento.pageY - lienzo.offsetTop;
pincel.fillStyle = colors[indiceColor];
pincel.beginPath();
pincel.arc(x,y,10,0,2*3.14);
pincel.fill();
console.log(x + "," + y);
}
function alterarColor() {
indiceColor++;
if (indiceColor == 3) {
indiceColor = 0;
}
}
lienzo.onclick = dibujarCirculo;
lienzo.oncontextmenu = alterarColor;
