A passport is the key to getting into other countries. You might have noticed, maybe while waiting in the passport-control queue, that these travel documents come in only a few colours. In general, passports are only red, green, blue, or black, according to Hrant Boghossian, the vice president of marketing at the interactive passport database Passport Index . Passports do, however, come in different shades of each of the four main colour groups. "Within each colour hue, we see vast variations," Boghossian told Business Insider via email. "There are in fact many passport colours." The process for selecting colours There are "many possible scenarios" as to why countries opt for a particular colour, according to Boghossian. "Members of the European Union use burgundy, while Caricom states use blue passports," he said. Caricom , or the Caribbean Community and Common Market, includes 15 Caribbean countries and dependencies. The...