No, I've heard of this as well. You know how there's a field titled "Nationality" in passports? I used to think that was a no-brainer until I found out that it is possible for one country to issue a travel document to a person of a different nationality (i.e. an American "travel document" issued for a Bangladeshi with a green card, a Thai-issued travel document for, let's say, a Danish tourist who's lost his own passport, etc.) which can be used to partially replace a national passport.

Apparently, these are green when issued by the US.