SchmeckFlyer

I do not have one, but know three people who do. In the US, two types of official passports are issued: diplomatic (black) and official (red).

It basically can only be used for official or authorized travel related to duties representing a state abroad, or the carrying out of duties by a government employee while abroad. When traveling for personal reasons or not in the function of representing a foreign state, a normal/personal passport (usually) must be employeed. The often-held idea that holders of diplomatic passports can travel around risk-free and untouched may actually be incorrect in that regard.

The main benefit of a diplomatic passport, however, seems to be that when traveling on one, authorities cannot search baggage or hinder the entry of the passport holder. Many airports have diplomatic channels at customs/immigration. I suppose this falls under the old diplomatic immunity privileges enjoyed by foreign representatives.

Upon cessation of official duties, a diplomatic or official passport will expire. Only former prominent government officials (ex-head of states, cabinet members) customarily receive a coutesy diplomatic passport after ending their official duties.