createCanvas(400, 400);

  frameRate(1);

}

​

function draw() {

  background(0);

  fill(colorFromPalette());

  ellipse(100, 200, 100);

  fill(colorFromPalette());

  ellipse(200, 200, 100);

  fill(colorFromPalette());

  ellipse(300, 200, 100);

}

​

function colorFromPalette() {

  let r = random();  

  if (r < 0.33) {  // three choices with equal odds

    return 'Coral';

  } else if (r < 0.66) {

    return 'SpringGreen';

  } else {         // implicit: 0.66 <= r

    return 'Yellow';

  }

}

​