code: function(color, amount) {
      var hsl = this.toHSL(color);
  
      hsl.s += amount / 100;
      hsl.s = clamp(hsl.s);
      return hsla(hsl);
    }
docs: Saturate or desaturate a color by a given amount
  
  @param {Color} color
  @param {Number} amount
  @returns {Color} color