To solve this question, the user needs to know the format of the Hex color code and the order of values it represents.

The Hex color code is a 6-digit representation of Red, Green, and Blue (RGB) values of a color. Each pair of digits represents the intensity of Red, Green, and Blue, respectively. The first two digits represent the intensity of Red, the second two digits represent Green, and the last two digits represent Blue.

Going through each option:

A. #GGRRBB: This option is incorrect because it has a different order of values than the Hex color code. The correct order is #RRGGBB, where RR represents the intensity of Red, GG represents the intensity of Green, and BB represents the intensity of Blue.

B. #RRBBGG: This option is incorrect because it has a different order of values than the Hex color code. The correct order is #RRGGBB, where RR represents the intensity of Red, GG represents the intensity of Green, and BB represents the intensity of Blue.

C. #RRGGBB: This option is correct. The order of values in the Hex color code is #RRGGBB, where RR represents the intensity of Red, GG represents the intensity of Green, and BB represents the intensity of Blue. In this case, FF represents the maximum intensity of Red, 99 represents the intensity of Green, and 66 represents the intensity of Blue.

D. #BBRRGG: This option is incorrect because it has a different order of values than the Hex color code. The correct order is #RRGGBB, where RR represents the intensity of Red, GG represents the intensity of Green, and BB represents the intensity of Blue.

Therefore, the correct answer is:

The Answer is: C. #RRGGBB