let xSpeed = 5;

let colorr = 127.5; // Midpoint of color range

let colorSpeed;

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

​

  fill(colorr);

  ellipse(x, 200, 30, 30);

  colorSpeed = (255 * xSpeed) / width;

  x += xSpeed;

​

  colorr += colorSpeed;

​

  if (x > width || x < 0) {

    xSpeed *= -1;

    colorSpeed *= -1;

  }

​

  colorr = constrain(colorr, 0, 255);

}

​