code: function(color1, color2, amount) {
      var p = amount / 100.0;
      var w = p * 2 - 1;
      var hsl1 = this.toHSL(color1);
      var hsl2 = this.toHSL(color2);
      var a = hsl1.a - hsl2.a;
  
      var w1 = (((w * a == -1) ? w : (w + a) / (1 + w * a)) + 1) / 2.0;
      var w2 = 1 - w1;
  
      var rgb = [
          color1[0] * w1 + color2[0] * w2,
          color1[1] * w1 + color2[1] * w2,
          color1[2] * w1 + color2[2] * w2
      ];
  
      var alpha = color1[3] * p + color2[3] * (1 - p);
      rgb[3] = alpha;
      return rgb;
    }
docs: Mix two colors.
  @param {Color} color1
  @param {Color} color2
  @param {Number} degrees
  @returns {Color} output