var hex = Number(rgb).toString(16);
  if (hex.length < 2) {
       hex = "0" + hex;
  }
  return hex;
};
var fullColorHex = function(r,g,b) {
  var red = rgbToHex(r);
  var green = rgbToHex(g);
  var blue = rgbToHex(b);
  return red+green+blue;
};

console.log(fullColorHex(10, 20, 30));