docs: function colorBlend(mode) {
      return function(first, second) {
          first = Color.color(first);
          second = Color.color(second);
          var ab = first.rgba[3];
          var as = second.rgba[3];
          var ar = as + ab * (1 - as);
          var rgba = [ 0, 0, 0, ar ]; // result
  
          var cb, cs, cr;
          for (var i = 0; i < 3; i++) {
              cb = first.rgba[i] / 255;
              cs = second.rgba[i] / 255;
              cr = mode(cb, cs);
              if (ar) {
                  cr = (as * cs + ab * (cb - as * (cb + cs - cr))) / ar;
              }
              rgba[i] = Math.round(cr * 255);
          }
          return Color.color(rgba);
      }
  }