code: function randCol (r, g, b, a) {
    return "rgba(" + Math.floor(Math.random() * r).toString() + "," +
                     Math.floor(Math.random() * g).toString() + "," +
                     Math.floor(Math.random() * b).toString() + "," + a + ")";
  }
docs: quietflow.js
  Paul Krishnamurthy 2016
  
  https://paulkr.com
  paul@paulkr.com