OBSERVATIONS
the official is wearing emotionless face despite the jubilant atmosphere
it is set during night-time with an impressive display of fireworks
there are vibrant colors all over the place except for the stoic guard wearing very drab attire
INFERRENCES
You can infer from the guards very official stance and clothes that he is representing a country that wants to take itself seriously.The fireworks can be perceived as multiple things. They can be viewed as a celebration of china's growth or they can be shown as a contrast, where china is remaining calm and formal during "funtime". As if they're saying "we're adults and we are not going to be cought up in some trivial game, we are a super power that takes itself seriously".
This same contrast is shown with the bright colored festivities and the guard's drab uniform. I think the whole point that China is making is that they are the world's most prominent force. Everything they do is grand and powerful, and no other nation can match their might.