Segregation was a major headache for the State Department from post-WW2 until the passage of the Civil Rights Act. They spent a lot of time soothing ruffled feathers of African diplomats - it was quite common for them to be harassed when travelling between Washington and the UN, particularly when passing through Delaware. Not to mention the problems organizing things like lunch meetings in segregated DC. State advocated strongly for the passage of the Civil Rights Act because of this; they argued for it as a national security issue, since the US wanted the countries sending these black diplomats as allies in the Cold War.

A source article on this: "No Diplomatic Immunity: African Diplomats, the State Department, and Civil Rights, 1961-1964" by Renee Romano, The Journal of American History. You can access it free online.

In the memoir "Down These Mean Streets" the Harlem/Puerto Rican author, Piri Thomas, describes going down south with another dark skinned Puerto Rican-American friend and pretending to be rich foreigners who barely spoke english in order to get service in a segregated restaurant.

According to the book this ruse worked until Piri (who was a huge trouble maker) thanked the waitress in exaggerated african american english. If my memory serves they had get out of dodge as soon as they were discovered to be Americans.

I would not characterise Maori or other Pacific Islanders as "black".