let w;

let swSize = 360 / numSwatches;

let off = 0;

function setup() {

  createCanvas(800, 400);

  colorMode(HSB, 360, 100, 100); //color wheel;saturation;brightness

  w = width / numSwatches;

  noStroke();

}

​

function draw() {

  background(220);

  off++;

  for (let sw = 0; sw < numSwatches; sw++) {

    let x = sw * w;

    let h = sw * swSize + off;

    h %= 360;

    fill(h, 100, 100);

​

    rect(x, 0, width / 36, height);

  }

}

​