Blue covers are for regular passports, red ones identify you in other countries as an agent on the US Government and say either "Official" or "Diplomatic" across the top in gold letters.
It helps if you get in some kinds of trouble abroad, but hurts in other ways (makes one a target for bad guys, and many governments require visas who wouldn't with a blue passport). I have to get a visa for both Spain and Japan, for instance, although the latter will be valid until the passport expires.
Theoretically, with a red passport once can refuse US Customs (inter-Agency privliges)but NASA instructs us to not do so except in emergencies. It does let one use the special diplomatic line in places like NYC when entering the US, which is often shorter.
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It helps if you get in some kinds of trouble abroad, but hurts in other ways (makes one a target for bad guys, and many governments require visas who wouldn't with a blue passport). I have to get a visa for both Spain and Japan, for instance, although the latter will be valid until the passport expires.
Theoretically, with a red passport once can refuse US Customs (inter-Agency privliges)but NASA instructs us to not do so except in emergencies. It does let one use the special diplomatic line in places like NYC when entering the US, which is often shorter.