黃中 = being employed as an imperial government official/having a career in the imperial government? Many Chinese clans have a "昭穆", a kind of poem from which each generation of the clan picks a successive character as a prefix to given names, so we can easily identify people from one generation to another. For instance, I am of the "性" generation according to my clan's "昭穆". Now, the "昭穆" contains this sentence:


  黃中元吉迪，青簡大名留。


According to this page, "黃中" would mean "being employed as an imperial government official" or "having a career in the imperial government" ("在朝為官"). However, I have been unable to find further reference to back up that interpretation. I have even looked up the character "黃" in the 《古漢語常用字字典》 and the closest thing I get is "[matters] related to the Emperor", with no direct mention of "government" or "officials".

Would somebody with good knowledge in classical Chinese be able to enlighten me?
黃中 means the emperor, not the employment, and 黃中元吉迪 means the emperor along with the nation becomes better and better.

It is the result, and via this the sentence would express the idea that it's a pleasure of your contributions to the nation.

So it concludes that the person is a government employee.